ATMOS ENERGY CORP
8-K, 1996-07-24
NATURAL GAS DISTRIBUTION
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<PAGE>
 
                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.. 20549

                                   FORM 8-K

                                CURRENT REPORT
                    Pursuant to Section 13 or 15(d) of the
                        Securities Exchange Act of 1934

Date of Report (Date of earliest event reported)          July 19, 1996
                                                          -------------

                            ATMOS ENERGY CORPORATION
- --------------------------------------------------------------------------
             (Exact name of registrant as specified in its charter)


     TEXAS                         0-11249                   75-1743247
- --------------------------------------------------------------------------
(State or other jurisdiction     (Commission                (IRS Employer
  of incorporation)               File Number)         Identification No.)
 

1800 Three Lincoln Centre, 5430 LBJ Freeway, Dallas, Texas     75240
- -------------------------------------------------------------------------
       (Address of principal executive offices)                (Zip Code)


Registrant's telephone number, including area code:       (214) 934-9227
                                                          --------------


- ------------------------------------------------------------------------
         (Former name or former address, if changes since last report)
<PAGE>
 
Item 5. Other Events.
        -------------

     On July 19, 1996, Atmos Energy Corporation ("Atmos") entered into a
definitive Agreement and Plan of Reorganization (the "Reorganization Agreement")
with United Cities Gas Company ("United Cities") whereby United Cities will be
merged with and into Atmos in a tax-free reorganization to be accounted for as a
pooling of interests.  All of the outstanding shares of common stock, no par
value, of United Cities will be exchanged for newly issued shares of common
stock, no par value, of Atmos on a share-for-share (1:1) basis.  Atmos will be
the surviving corporation in the merger. Consummation of the merger is subject
to certain terms and conditions set forth in the Reorganization Agreement,
including shareholder approval from the shareholders of Atmos and United Cities
and approval from certain state and federal regulatory authorities.  As of June
30, 1996, Atmos had 15,982,304 shares of its common stock outstanding, and
United Cities had 13,102,913 shares of its common stock outstanding.

     The Board of Directors of Atmos received the opinion of Merrill Lynch,
Pierce, Fenner & Smith Incorporated to the effect that the exchange ratio is
fair, from a financial point of view, to Atmos and its shareholders.

     The foregoing is qualified in its entirety by reference to the
Reorganization Agreement, a copy of which is attached as an exhibit hereto and
which is incorporated by reference herein.  The Reorganization Agreement
contains provisions with respect to the conditions to closing and termination
provisions.

     Atmos is a natural gas utility engaged in the distribution and sale of
natural gas to approximately 673,000 residential, commercial, industrial,
agricultural, and other customers in Texas, Louisiana, Kentucky, Colorado,
Kansas, and Missouri.  United Cities is a natural gas utility engaged in the
distribution and sale of natural gas to approximately 310,000 customers in
Tennessee, Illinois, Virginia, Kansas, Missouri, South Carolina, Georgia, and
Iowa, and in the sale of propane in the states of Tennessee, Virginia and North
Carolina. United Cities' assets consist of the property, plant and equipment
used in its natural gas and propane sales and distribution businesses. Following
consummation of the merger, Atmos intends to continue to operate the United
Cities business as a division of Atmos, along with Atmos' Energas Company, Trans
Louisiana Gas Company, Western Kentucky Gas Company, and Greeley Gas Company
divisions.
<PAGE>
 
Item 7.   Financial Statements and Exhibits.
          ----------------------------------

          See the Exhibits Index for a list of exhibits filed with this report.

                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.

                                    ATMOS ENERGY CORPORATION


Date:  July 24, 1996               By: /s/ James F. Purser
                                       --------------------
                                         James F. Purser
                                         Executive Vice President 
                                         and Chief Financial Officer
<PAGE>
 
                                 EXHIBITS INDEX



Exhibit
Number    Description
- ------    -----------

2.1       Agreement and Plan of Reorganization, dated as of July 19, 1996, by
          and between Atmos Energy Corporation and United Cities Gas Company

2.2       List of exhibits omitted from Exhibit 2.1

4.1       Restated Articles of Incorporation of Atmos, as amended as of February
          9, 1995 (incorporated by reference to Exhibit 3.1 to Form 10-K for
          fiscal year ended September 30, 1995, File No. 1-10042)

4.2       By-Laws of Atmos Energy Corporation (As amended as of November 9,
          1994) (incorporated by reference to Exhibit 3.2 to Form 10-K for
          fiscal year ended September 30, 1995, File No. 1-10042)

4.3       Specimen Common Stock Certificate (Atmos Energy
          Corporation)(incorporated by reference to Exhibit (4)(b) of Form 10-K
          for fiscal year ended September 30, 1988, File No. 1-10042)

4.4       Rights Agreement, dated as of April 27, 1988, between Atmos and Morgan
          Shareholder Services Trust Company (incorporated by reference to
          Exhibit (1) of Form 8-K filed May 10, 1988, File No. 0-11249)

4.5       Amendment No. 1 to Rights Agreement, dated August 10, 1994
          (incorporated by reference to Exhibit 4.3(b) of Form 10-K for fiscal 
          year ended September 30, 1994, File No. 1-10042)

4.6       Certificate of Adjusted Price, dated August 15, 1994 (incorporated by
          reference to Exhibit 4.3(c) of Form 10-K for fiscal year ended
          September 30, 1994, File No. 1-10042)

20.1      Press release, dated July 22, 1996

99.1      Standstill Agreement, dated as of July 13, 1996, between Atmos Energy
          Corporation and United Cities Gas Company

<PAGE>
 

                                                                     EXHIBIT 2.1


                      AGREEMENT AND PLAN OF REORGANIZATION


     THIS AGREEMENT AND PLAN OF REORGANIZATION (this "Agreement") is made and
entered into this 19th day of July, 1996, by and between ATMOS ENERGY
CORPORATION, a Texas corporation ("Atmos"), and UNITED CITIES GAS COMPANY, an
Illinois and Virginia corporation ("United Cities").

     In consideration of the mutual agreements herein contained, Atmos and
United Cities agree to carry out a plan of reorganization providing for a
statutory merger under the applicable laws of Texas, Illinois and Virginia
whereby:

     A.  United Cities will be merged with and into Atmos, with Atmos as the
surviving corporation incorporated and existing under the laws of the States of
Texas and Virginia;

     B.  the shareholders of United Cities, upon exchange of their shares of
common stock of United Cities, will receive shares of common stock of Atmos; and

     C.  all of the assets, properties, and business of United Cities, together
with all of the obligations and liabilities of United Cities,  shall thereupon
be transferred to and assumed by Atmos;

all subject to the following terms and conditions:

                                   ARTICLE 1

                REPRESENTATIONS AND WARRANTIES OF UNITED CITIES

     United Cities hereby represents and warrants to Atmos that the statements
set forth in this Article 1 are true, correct and complete as of the date of
this Agreement and will be true, correct and complete as of the Closing Date as
though made then and as though the Closing Date were substituted for the date of
this Agreement throughout this Article 1, except as otherwise set forth in the
United Cities Disclosure Schedule attached hereto as Exhibit A; provided, that
each matter set forth in the United Cities Disclosure Schedule shall be deemed
to be an exception only to those representations and warranties that are
specifically referenced by Section number in the United Cities Disclosure
Schedule in connection with such matter.

     Section 1.1  Organization and Qualification.
     -----------  ------------------------------ 

          (a)  United Cities is a corporation duly organized, validly existing,
     and in good standing under the laws of the jurisdictions of its
     incorporation and has all requisite corporate power and authority and
     possesses all franchises, grants, authorizations, licenses, permits,
     easements, consents, certificates, approvals, and orders (collectively,
     "Governmental Authorizations") necessary to own, lease, and operate its
     properties and assets and to carry on its business as it is now being
     conducted except where the failure 

                                       1
<PAGE>
 
     to have any of such Governmental Authorizations would not have a material
     adverse effect on the business, operations, properties, condition
     (financial or otherwise), assets or liabilities, of the United Cities
     Entities, taken as a whole. United Cities is duly qualified or licensed as
     a foreign corporation to do business, and is in good standing, in each
     jurisdiction in which the character of the property owned, leased, or
     operated by it or the nature of the business conducted by it makes such
     qualification or licensing necessary, except in such jurisdictions (if any)
     where the failure to be duly qualified or licensed does not and would not
     have a material adverse effect on the business, operations, properties,
     condition (financial or otherwise), assets or liabilities, of the United
     Cities Entities, taken as a whole.

          (b)  United Cities has not been a subsidiary or division of another
     corporation or entity at any time during the two-year period prior to the
     date of this Agreement.

          (c)  United Cities has heretofore delivered to Atmos true, correct, 
     and complete copies of United Cities' Articles of Incorporation and Bylaws,
     including all amendments thereto.

     Section 1.2  Subsidiaries.
     -----------  ------------ 

          (a)  United Cities does not directly or indirectly own any equity or
     similar interest in any corporation, partnership, joint venture, or other
     business association or entity, except as set forth in Section 1.2(b),
     other than (i) United Cities Energy Corporation, a Delaware corporation
     that is wholly owned by United Cities, (ii) United Cities Gas Storage
     Company, a Delaware corporation that is wholly owned by United Cities,
     (iii) United Cities Propane Gas of Tennessee, Inc., a Tennessee corporation
     that is wholly owned by United Cities Energy Corporation, and (iv) United
     Cities Leasing, Inc., a Georgia corporation that is wholly owned by United
     Cities Energy Corporation (collectively, the "United Cities Subsidiaries").
     (United Cities and the United Cities Subsidiaries are referred to
     collectively in this Agreement as the "United Cities Entities.")  United
     Cities is the sole record and beneficial owner of, and has good and valid
     title to, all of the outstanding shares of capital stock of United Cities
     Energy Corporation and United Cities Gas Storage Company, and United Cities
     Energy Corporation is the sole record and beneficial owner of, and has good
     and valid title to, all of the outstanding capital stock of United Cities
     Propane Gas of Tennessee, Inc. and United Cities Leasing, Inc., in each
     case free and clear of all liens, mortgages, pledges, security interests or
     other encumbrances.  All of the outstanding capital stock of each of the
     United Cities Subsidiaries has been duly authorized and validly issued, is
     fully paid and nonassessable.

          (b)  United Cities Energy Corporation owns a 45% equity interest in
     Woodward Marketing, L.L.C., free and clear of all liens, mortgages,
     pledges, security interests and other encumbrances.  The equity ownership 
     interest held by United Cities Energy

                                       2
<PAGE>
 
     Corporation in Woodward Marketing, L.L.C. has been duly authorized and
     validly issued, is fully paid and nonassessable.

          (c)  Each of the United Cities Subsidiaries is a corporation duly
     organized, validly existing, and in good standing under the laws of the
     jurisdiction of its incorporation and has all requisite corporate power and
     authority and possesses all Governmental Authorizations necessary to own,
     lease, and operate its properties and assets and to carry on its business
     as it is now being conducted except where the failure to have any of such
     Governmental Authorizations would not have a material adverse effect on the
     business, operations, properties, condition (financial or otherwise),
     assets or liabilities, of the United Cities Entities, taken as a whole.
     Each of the United Cities Subsidiaries is duly qualified or licensed as a
     foreign corporation to do business, and is in good standing, in each
     jurisdiction in which the character of the property owned, leased, or
     operated by it or the nature  of the business conducted by it makes such
     qualification or licensing necessary, except in such jurisdictions (if any)
     where the failure to be duly qualified or licensed does not and would not
     have a material adverse effect on the business, operations, properties,
     condition (financial or otherwise), assets or liabilities of the United
     Cities Entities, taken as a whole.

          (d)  Woodward Marketing, L.L.C. is a limited liability company duly
     organized, validly existing and in good standing under the laws of the
     State of Delaware and has all requisite limited liability company power and
     authority to own, lease, and operate its properties and assets and to carry
     on its business as it is now being conducted and is duly qualified as
     foreign limited liability company in the State of Texas.

          (e)  United Cities has heretofore delivered to Atmos true, correct and
     complete copies of the Articles of Incorporation and Bylaws, including all
     amendments thereto, of the United Cities Subsidiaries, and of the charter
     documents and Limited Liability Company Agreement of Woodward Marketing,
     L.L.C.

     Section 1.3  Capitalization.  The entire authorized capital stock of United
     -----------  --------------                                                
Cities consists of 40,000,000 shares of common stock, no par value ("United
Cities Stock"), and 200,000 shares of preferred stock, no par value ("Preferred
Stock").  As of June 30, 1996, (a) 13,102,913 shares of United Cities Stock were
issued and outstanding, all of which were duly authorized, validly issued, fully
paid, and nonassessable and free of preemptive rights, (b) no shares of
Preferred Stock were issued and outstanding, and (c) no shares of United Cities
Stock or Preferred Stock were held in the treasury of United Cities.  Except as
set forth on the United Cities SEC Reports, there are no options, warrants, or
other rights, agreements, arrangements, or commitments of any character relating
to the issued or unissued capital stock of the United Cities Entities or
obligating the United Cities Entities to issue or sell any shares of capital 
stock of, or any securities convertible into or evidencing the right to purchase
any shares of capital stock of or other equity interests in, the United Cities
Entities. There are no obligations, contingent or otherwise, of the 

                                       3
<PAGE>
 
United Cities Entities to repurchase, redeem, or otherwise acquire any shares of
capital stock or other equity interests in any of the United Cities Entities.

     Section 1.4  Authority Relative to this Agreement.  United Cities has all
     -----------  ------------------------------------                        
requisite corporate power and authority to execute and deliver this Agreement
and to perform its obligations hereunder and to consummate the transactions
contemplated hereby, subject to the approval of United Cities shareholders as
contemplated in this Agreement and the terms and conditions of this Agreement.
The execution and delivery of this Agreement by United Cities and the
consummation by United Cities of the transactions contemplated hereby have been
duly and validly authorized by United Cities' Board of Directors and, except for
the approval of the shareholders of United Cities, no other corporate
proceedings on the part of United Cities are necessary to authorize this
Agreement or to consummate the transactions so contemplated.  This Agreement has
been duly and validly executed and delivered by United Cities and constitutes
the legal, valid, and binding obligation of United Cities and is enforceable
against United Cities in accordance with its terms, subject to bankruptcy,
insolvency, moratorium and other laws generally affecting creditors' rights.

     Section 1.5  No Conflict; Required Filings and Consents.  The execution,
     -----------  ------------------------------------------                 
delivery, and performance of this Agreement by United Cities and the
consummation by United Cities of the transactions contemplated hereby in
accordance with the terms and conditions hereof, including the Merger, do not
and will not:

          (a)  conflict with the Articles of Incorporation or Bylaws of the
     United Cities Entities or the Certificate of Formation or Limited Liability
     Company Agreement of Woodward Marketing, L.L.C.;

          (b)  conflict with or violate any law, rule, regulation, order,
     judgment, or decree applicable to any of the United Cities Entities or by
     which any of them or any of their respective properties is bound or
     affected;

          (c)  except for those consents and waivers required to be obtained
     pursuant to Section 3.5, require from any person other than a governmental
     or regulatory authority any consent, approval, or notice under, or violate,
     result in any breach of, constitute a default (or an event that with notice
     or lapse of time or both would become a default) under, or give to others
     any rights of termination, amendment, acceleration, or cancellation of, or
     result in the creation of a lien or encumbrance on any of the property or
     assets of any of the United Cities Entities pursuant to, any note, bond,
     mortgage, indenture, contract, agreement, lease, license, or other
     instrument or obligation to which any of the United Cities Entities is a
     party or by which any of the United Cities Entities or any of their
     respective properties is bound or affected; or

          (d)  require any consent, approval, authorization, or permit of, or
     filing with or notification to, any governmental or regulatory authority
     except (i) the applicable  

                                       4
<PAGE>
 
     requirements of federal and state securities laws, (ii) the filing
     requirements under the Hart-Scott-Rodino Act, (iii) the filing and
     recordation of appropriate merger or other documents as required by the
     Texas Business Corporation Act, the Illinois Business Corporation Act, and
     the Virginia Stock Corporation Act, (iv) approvals of the applicable state
     public utility commissions in the states in which United Cities or Atmos is
     doing business, and (v) approval of the Federal Energy Regulatory
     Commission.

     Section 1.6  Compliance.  None of the United Cities Entities is in breach,
     -----------  ----------                                                   
default, or violation of, and no event has occurred or is occurring that with
notice or lapse of time or both would become a breach, default, or violation of,
(a) any of the United Cities Entities' Articles of Incorporation or Bylaws or
the Certificate of Formation or Limited Liability Company Agreement of Woodward
Marketing, L.L.C., (b) any law, rule, regulation, order, judgment, or decree
applicable to any of the United Cities Entities or by which any of them or any
of their respective properties is bound or affected, or (c) any note, bond,
mortgage, indenture, contract, agreement, lease, license, permit, franchise, or
other instrument or obligation to which any of the United Cities Entities is a
party or by which any of them or any of their respective properties is bound or
affected, nor have any of them received and not finally resolved any complaint,
citation, or notice of a breach, default, or violation of any of the foregoing
nor are any threatened.

     Section 1.7  Environmental Matters.
     -----------  --------------------- 

          (a)  No Hazardous Materials are now located in, on, at, upon, or under
     the Subject Property currently owned or operated by any of the United
     Cities Entities or have migrated or emanated, or threaten to migrate or
     emanate, to adjacent property in a quantity or manner that is required to
     be reported under any Environmental Requirements, or that is in violation
     of any Environmental Requirements, or for which any of the United Cities
     Entities will be liable under any Environmental Requirements for the cost
     of remediation or other response if such costs are incurred by an
     Environmental Agency; and no Hazardous Materials have been located in, on,
     at, upon, or under the Subject Property, or migrated or emanated from the
     Subject Property at any time prior to or during the Use of the Subject
     Property by any of the United Cities Entities in a quantity or manner that
     is required to be reported under any Environmental Requirements, or that is
     in violation of any Environmental Requirements, or for which any of the
     United Cities Entities will be liable under any Environmental Requirements
     for the cost of remediation or other response if such costs are incurred by
     an Environmental Agency.

          (b)  No Hazardous Materials have been generated, stored, transported,
     disposed of on-site, or sent off-site from, in, on, at, or upon the Subject
     Property at any time during the Use of the Subject Property by any of the
     United Cities Entities (or prior to the Use of the Subject Property by any
     of the United Cities Entities) in a quantity or manner that is required to
     be reported under any Environmental Requirements, or that is in violation
     of any Environmental Requirements, or for which any of the United Cities
     Entities will 

                                       5
<PAGE>
 
     be liable under any Environmental Requirements for the cost of remediation
     or other response if such costs are incurred by an Environmental Agency.

          (c)  There are no off-site locations where Hazardous Materials
     generated or transported from the Subject Property have been stored,
     treated, recycled, or disposed of by any of the United Cities Entities or
     their agents, employees, or representatives in a quantity or manner that is
     required to be reported under any Environmental Requirements, or that is in
     violation of any Environmental Requirements, or for which any of the United
     Cities Entities will be liable under any Environmental Requirements for the
     cost of remediation or other response if such costs are incurred by an
     Environmental Agency.

          (d)  Each of the United Cities Entities has all permits, licenses, or
     authorizations from any  Environmental Agency that it is required to have
     by any Environmental Requirement in order to operate any aspect of the
     Subject Property currently operated by it or the business currently
     conducted at the Subject Property; the Use of the Subject Property
     currently Used by each of the United Cities Entities, including but not
     limited to any and all Environmental Activity, and all Environmental
     Conditions, is and has been in compliance with all Environmental
     Requirements during the Use of the Subject Property by each of the United
     Cities Entities and at all times prior to its Use by each of the United
     Cities Entities.

          (e)  No Environmental Costs have been suffered by any of the United
     Cities Entities or by any third party prior to or during the Use of the
     Subject Property by any of the United Cities Entities, and United Cities is
     not aware of, and has not received notice of, any past or present events,
     conditions, circumstances, activities, practices, incidents, actions, or
     plans that may result in Environmental Costs or that may give rise to any
     common law or legal liability based on or related to the manufacture,
     processing, distribution, use, treatment, storage, disposal, transport, or
     handling or the emission, discharge, release, or threatened release into
     the environment, of any pollutant, contaminant, chemical, or industrial
     toxic or hazardous substance or waste or Hazardous Materials.

          (f)  None of the United Cities Entities has Used, in the past, any
     facilities that could reasonably be expected to subject any of the United
     Cities Entities to  Environmental Costs.

          (g)  All of the manufactured gas plants now or formerly Used by any 
     of the United Cities Entities and all locations where waste from these
     plants was disposed of are set forth in the United Cities SEC Reports.

          (h)  All of the underground storage tanks located on the Subject
     Property are set forth in the United Cities SEC Reports.

                                       6
<PAGE>
 
     Section 1.8  Contracts.  United Cities has made available to Atmos all
     -----------  ---------                                                
material contracts, loan agreements, indentures, commitments, and other
agreements or documents to which any of the United Cities Entities is a party or
by which any of the United Cities Entities or any of their respective properties
is bound or affected.  All such contracts and instruments are in full force and
effect and no party thereto is in default thereunder and no default is
threatened thereunder.

     Section 1.9  SEC Filings; Financial Statements; Absence of Undisclosed
     -----------  ---------------------------------------------------------
Liabilities.
- ----------- 

          (a)  United Cities has filed all forms, reports, and documents 
     required to be filed with the SEC since January 1, 1993, and has heretofore
     delivered or made available to Atmos, in the form filed with the SEC, (i)
     its Annual Reports on Form 10-K for the fiscal years ended December 31,
     1993 through 1995, (ii) its Quarterly Report on Form 10-Q for the period
     ended March 31, 1996, (iii) all proxy statements relating to United Cities'
     meetings of shareholders (whether annual or special) held since January 1,
     1993, (iv) all Forms 8-K filed by United Cities with the SEC since January
     1, 1993, (v) all other reports or registration statements filed by United
     Cities with the SEC since January 1, 1993, and (vi) all amendments and
     supplements to all such reports, registration statements and proxy
     statements filed by United Cities with the SEC since January 1, 1993
     (collectively, the "United Cities SEC Reports"). As of their respective
     dates, the United Cities SEC Reports were prepared in substantial
     compliance with the requirements of the Securities Act or the Exchange Act,
     as the case may be, and did not at the time they were filed contain any
     untrue statement of a material fact or omit to state a material fact
     required to be stated therein or necessary in order to make the statements
     therein, in the light of the circumstances under which they were made, not
     misleading. None of the United Cities Entities other than United Cities is
     subject to the reporting requirements of the Exchange Act.

          (b)  United Cities has heretofore delivered or made available to Atmos
     its audited consolidated financial statements for its fiscal years ended
     December 31, 1993 through 1995 and its unaudited consolidated financial
     statements for the period ended March 31, 1996.  All such financial
     statements of United Cities that have been delivered or made available to
     Atmos have been prepared in accordance with generally accepted accounting
     principles applied (except as otherwise noted therein) on a consistent
     basis throughout the periods covered thereby (subject, in the case of
     any such financial statements that are unaudited, to year-end adjustments
     in such amount and of such type as are or will be consistent with
     adjustments made in prior fiscal years).  The consolidated financial
     statements (together with the related notes thereto) fairly present in all
     material respects the consolidated financial condition and consolidated
     results of operation of United Cities as of and for the respective dates
     indicated.

          (c)  None of the United Cities Entities has any liabilities or
     obligations (whether accrued, absolute, contingent, known or unknown, or
     otherwise) that (i) are not accrued or reserved against in the consolidated
     balance sheet of United Cities as at March 31, 1996 

                                       7
<PAGE>
 
     or reflected in the notes thereto in accordance with generally accepted
     accounting principles consistently applied or (ii) were incurred after the
     date of such balance sheet outside of the ordinary course of business of
     any of the United Cities Entities.

     Section 1.10  Books and Records.  United Cities has made available to
     ------------  -----------------                                      
Atmos, and will continue to make available to Atmos, all of the United Cities
Entities' books, records, and certificates.  All of such books, records, and
certificates are true, complete, and correct.

     Section 1.11  Conduct of Business in Ordinary Course; Absence of Certain
     ------------  ----------------------------------------------------------
Changes or Events.  Since March 31, 1996, each of the United Cities Entities has
- -----------------                                                               
conducted its business only in the ordinary course; and, since such date, there
has not been any adverse change in the business, operations, properties,
condition (financial or otherwise), assets or liabilities of any of the United
Cities Entities, taken as a whole, or any condition, event, or development that
will result in an adverse change in the business, operations, properties,
condition (financial or otherwise), assets or liabilities of the United Cities
Entities, taken as a whole.

     Section 1.12  Litigation.  There are no material claims, actions, suits,
     ------------  ----------                                                 
investigations, or proceedings pending or threatened against or affecting any of
the United Cities Entities or any of their respective properties or rights at
law or in equity before or by any court, arbitrator, or administrative,
governmental, or regulatory authority or body.  None of the United Cities
Entities nor any of their respective properties is subject to any order, writ,
judgment, injunction, decree, determination, or award.

     Section 1.13  Title to, and Condition of, Assets.  Each of the United
     ------------  ----------------------------------                     
Cities Entities has good and marketable title to, or a valid leasehold interest
in, all of its assets and properties, real and personal, including the
properties, assets, and leasehold interests reflected in the United Cities
balance sheet dated March 31, 1996 referred to in Section 1.9 of this Agreement
(except for any properties or assets disposed of in the ordinary course of
business since the date of such balance sheet), necessary or appropriate for the
operation of its business, free and clear of all liens, mortgages, pledges,
security interests, or other encumbrances (except for matters set forth in the
notes to such balance sheet and the notes to the December 31, 1995 balance
sheet). All of the United Cities Entities' properties and assets are in good
condition and repair (ordinary wear and tear excepted) and are adequate and
sufficient for the conduct of the United Cities Entities' businesses.

     Section 1.14  Intellectual Property.  The United Cities Entities own or
     ------------  ---------------------                                    
possess, or can acquire on reasonable terms, the patents, patent rights,
licenses, inventions, copyrights, know-how (including trade secrets and other
unpatentable proprietary or confidential information, systems or procedures),
trademarks, service marks and trade names presently employed by them in
connection with the business now operated by them, and none of the United Cities
Entities has received any notice of infringement of or conflict with asserted
rights of others with respect to any of the foregoing which, singly or in the
aggregate, if the subject of an unfavorable decision, ruling or finding, would
result in any material adverse change in the business, operations, properties,

                                       8
<PAGE>
 
condition (financial or otherwise), assets or liabilities of the United Cities
Entities, taken as a whole.

     Section 1.15  Taxes.  All Tax Returns of or relating to any Taxes that are
     ------------  -----                                                       
required to be filed with respect to United Cities and the United Cities
Subsidiaries or any of their income, properties, or operations have been duly
filed on a timely basis and were true, complete, and correct.  All Taxes
attributable to United Cities and the United Cities Subsidiaries or any of their
income, properties, or operations that are or were due and payable have been
timely paid, and United Cities and the United Cities Subsidiaries have no
liability for any Taxes other than with respect to their current taxable year
for which adequate provisions have been made and are reflected in United Cities'
consolidated financial statements in accordance with generally accepted
accounting principles.

     Section 1.16  Employee Benefit Plans.
     ------------  ---------------------- 

          (a)  United Cities has previously delivered or made available to Atmos
     true, correct and complete copies of (i) each Plan that is a "multiemployer
     plan," as defined in ERISA Section 4001, (ii) each other employee benefit
     plan as defined in Section 3(3) of ERISA with respect to which a United
     Cities Entity or any Group Member is a "Party in Interest," as defined in
     Section 3(14) of ERISA, and (iii) each other Employee Benefit Arrangement.

          (b)  Each United Cities Entity, each Group Member, and each Plan is
     now, and has been from its inception, in compliance with the provisions of
     ERISA and the Code insofar as ERISA and the Code are applicable to such
     Plans.  Each Plan intended to be qualified under Section 401(a) of the Code
     has been determined to be so qualified by the IRS and nothing has occurred
     since the date of the last such determination which resulted or is likely
     to result in the revocation of such determination.  All required reports
     and descriptions of each Plan have been timely filed and distributed as
     required by ERISA.

          (c)  There has not occurred with respect to any Plan any non-exempt
     "Prohibited Transaction," as defined in either Section 406 of ERISA or
     Section 4975 of the Code.

          (d)  There has not occurred with respect to any Plan any "Reportable
     Event," as defined in Section 4043 of ERISA.  No Plan has applied for or
     obtained a waiver from the IRS of any minimum funding requirement under
     Section 412 of the Code.

          (e)  (i) No Plan has been terminated, and no withdrawal from any
     "multiemployer plan," as defined in Section 4001 of ERISA, has occurred
     since the inception of any Plan under circumstances that have given rise
     to, or would give rise to, any actual or potential liability to the PBGC or
     any other person (excluding liabilities to participants (other than any
     liability for unpaid benefits) for benefits payable in the normal course of
     events pursuant to any such termination or withdrawal), (ii) no event or

                                       9
<PAGE>
 
     condition exists which presents a risk of termination of any Plan by the
     PBGC, and (iii) there is no actual or potential liability to the PBGC or
     any other person expected by the United Cities Entities or any Group Member
     to be incurred with respect to any Plan, including, but not limited to, any
     liability for premium payments, for any accumulated funding deficiency as
     defined in Section 302 of ERISA or for any minimum funding contribution
     under Section 302 of ERISA.

          (f)  The current value (as defined in Section 4062(b)(1)(A) of ERISA)
     of all accrued  benefits (as defined in Section 3 of ERISA) under each Plan
     which is a plan subject to the provisions of Title IV of ERISA does not, as
     of January 1, 1996, exceed the current value of the assets of such Plan
     allocable to such accrued benefits, by an amount which is more than
     $1,500,000.

          (g)  No lien imposed under Section 412(n) of the Code exists in favor
     of any Plan upon any property belonging to a Group Member.

          (h)  United Cities has previously delivered or made available to Atmos
     true, correct and complete copies of the annual reports and actuarial
     reports for the preceding two plan years (1993 and 1994) filed with respect
     to each such Plan and Employee Benefit Arrangement, summary plan
     descriptions and other communications to employees relating to each such
     Plan and Employee Benefit Arrangement, any related trust or third-party
     funding vehicle documents and related financial statements, and all letters
     from the IRS, if any, confirming the tax-exempt status or qualification
     under Section 401(a) of the Code of any Plan.  There are no Plans or
     Employee Benefit Arrangements other than those previously delivered and
     made available to Atmos.

          (i)  Neither (i) the United Cities Entities, or any director, officer,
     employee, or agent of a United Cities Entity, has, with respect to any
     Plan, nor (ii) any Plan or trust created thereunder or trustee or
     administrator thereof has, engaged in any conduct that would result in any
     penalties under Section 502(i) of ERISA or any liability under Section 409
     of ERISA for breach of fiduciary duty.  No civil or criminal action or
     claim (other than uncontested claims for benefits) is pending or threatened
     with respect to any Plan.

          (j)  None of the United Cities Entities, any Group Member, or any
     director, officer, or employee of any of the foregoing have taken any
     elective action that would commit a United Cities Entity to continue any
     Plan or Employee Benefit Arrangement or any benefit thereunder for any
     present or former employee of a United Cities Entity or that would prevent
     such United Cities Entity from changing or terminating any such benefit or
     plan; provided, that this representation shall not be construed to apply
     with respect to any express provision of a document which provides for such
     effect without further action or election by such persons.

                                       10
<PAGE>
 
          (k)  No United Cities Entity now has in effect, or previously had in
     effect, any welfare benefit plan, commitment, understanding, or arrangement
     providing for medical or death benefits (whether insured or uninsured) with
     respect to current or former employees beyond their date of retirement or
     other termination of service (other than coverage mandated by Section 4980B
     of the Code and Section 601 of ERISA, the cost of which is fully paid by
     the former employee or his or her dependents).

          (l)  For purposes of this Section 1.16, the terms "Employee Benefit
     Arrangement," "Group Member," and "Plan" shall be interpreted to exclude
     all reference to Atmos Entities under Section 8.1(l), (v) and (hh) hereof.

     Section 1.17  Labor Matters.   United Cities has previously delivered or
     ------------  -------------                                             
made available to Atmos true, correct and complete copies of all labor contracts
and collective bargaining agreements.  Except as set forth in the United Cities
SEC Reports, there are no employee activities or controversies (including, but
not limited to, any labor organizing activities, election petitions or
proceedings preparatory thereto, unfair labor practice complaints, labor
strikes, disputes, slowdowns, or work stoppages) pending or, to United Cities'
knowledge, threatened, between any of the United Cities Entities and any of
their employees.

     Section 1.18  Disclosure; Information in the Proxy Statement/Prospectus.
     ------------  ---------------------------------------------------------  
No representation or warranty by United Cities in this Agreement and no
statement contained in any certificate furnished or to be furnished by United
Cities to Atmos pursuant to the provisions of this Agreement contains or will
contain any untrue statement of material fact or omits or will omit to state any
material fact necessary, in light of the circumstances under
which it is made, in order to make the statements herein or therein not
misleading.  Any written information supplied by United Cities specifically for
inclusion or incorporation by reference in the Proxy Statement/Prospectus and
which is included or incorporated by reference therein shall not, at the date
the Proxy Statement/Prospectus (or any amendment thereof or supplement thereto)
is filed with the SEC, at the time of the Atmos Shareholders Meeting, at the
time of the United Cities Shareholders Meeting, and at the time the Proxy
Statement/Prospectus becomes effective with the SEC as a registration statement,
be false or misleading with respect to any material fact, omit to state any
material fact required to be stated therein or necessary in order to make the
statements made therein, in the light of the circumstances under which they are
made, not misleading, or omit to state any material fact necessary to correct
any statement in any earlier communication with respect to the solicitation of
proxies for the Atmos Shareholders Meeting or the United Cities Shareholders
Meeting that has become materially false or misleading.  If at any time prior to
the Effective Time any event relating to any of the United Cities Entities or
any of their respective directors or officers should be discovered by United
Cities which should be set forth in a supplement to the Proxy
Statement/Prospectus, United Cities shall promptly inform Atmos in writing.
Notwithstanding the foregoing, United Cities makes no representation or warranty
with respect to any information to be contained in the Proxy
Statement/Prospectus other than information provided in writing by United Cities
specifically for inclusion or incorporation by reference in the Proxy
Statement/Prospectus.

                                       11
<PAGE>
 
     Section 1.19  Insurance.  United Cities has not failed to give any notice
     ------------  ---------                                                  
or present any claim under any insurance policies or binders maintained by any
of the United Cities Entities with respect to their properties and business in
due and timely fashion.  None of the United Cities Entities has received notice
of cancellation or nonrenewal of any such policy or binder.

     Section 1.20  Broker's Fees.  No broker, finder, or investment banker
     ------------  -------------                                          
(other than PaineWebber Incorporated) is entitled to any brokerage, finder's, or
other fee or commission in connection with the transactions contemplated by this
Agreement based upon arrangements made by or on behalf of any of the United
Cities Entities.

     Section 1.21  No United Cities Investment in Atmos Stock.  None of the
     ------------  ------------------------------------------              
United Cities Entities  has acquired or is the beneficial owner of any Atmos
Stock.

     Section 1.22  Board Recommendation.  The Board of Directors of United
     ------------  --------------------                                   
Cities has, by resolutions duly adopted by the requisite vote of directors
present at a meeting of such Board duly called and held on July 19, 1996,
determined that the Merger in accordance with the terms of this Agreement and
the Plan of Merger is fair and in the best interests of its shareholders and has
recommended that the shareholders of United Cities approve the Merger and Plan
of Merger, and ratify this Agreement.

     Section 1.23  PUHCA.   Neither United Cities nor any other of the United
     ------------  -----                                                     
Cities Entities is required to register under PUHCA, or the rules and
regulations thereunder.

     Section 1.24  Regulation as a Utility.  United Cities is a regulated public
     ------------  -----------------------                                      
utility in the States of Tennessee, Illinois, Missouri, Georgia, South Carolina,
Virginia, Iowa, and Kansas and in no other state.  Neither United Cities nor any
United Cities Entity is subject to regulation as a public utility or public
service company (or similar designation) by any other state in the United
States, by the United States or any agency or instrumentality of the United
States or by any foreign country, other than the Federal Energy Regulatory
Commission.

     Section 1.25  Vote Required.  The approval of the Merger by holders of a
     ------------  -------------                                             
majority of the shares of outstanding United Cities Stock is the only vote of
the holders of any class or series of the capital stock of United Cities
required to approve this Agreement, the Plan of Merger, the Merger, and the
other transactions contemplated hereby.

     Section 1.26  Opinion of Financial Advisor.  United Cities has received the
     ------------  ----------------------------                                 
opinion of PaineWebber Incorporated, dated the date hereof, to the effect that,
as of the date hereof, the exchange ratio set forth in the Plan of Merger is
fair from a financial point of view to the holders of United Cities Stock.

                                       12
<PAGE>
 
                                   ARTICLE 2

                    REPRESENTATIONS AND WARRANTIES OF ATMOS

     Atmos hereby represents and warrants to United Cities that the statements
set forth in this Article 2 are true, correct and complete as of the date of
this Agreement and will be true, correct and complete as of the Closing Date as
though made then and as though the Closing Date were substituted for the date of
this Agreement throughout this Article 2, except as otherwise set forth in the
Atmos Disclosure Schedule attached hereto as Exhibit B; provided, that each
matter set forth in the Atmos Disclosure Schedule shall be deemed to be an
exception only to those representations and warranties that are specifically
referenced by Section number in the Atmos  Disclosure Schedule in connection
with such matter.

     Section 2.1  Organization and Qualification.
     -----------  ------------------------------ 

          (a)  Atmos is a corporation duly organized, validly existing, and in
     good standing under the laws of the jurisdictions of its incorporation and
     has all requisite corporate power and authority and possesses all
     franchises, grants, authorizations, licenses, permits, easements, consents,
     certificates, approvals, and orders (collectively, "Governmental
     Authorizations") necessary to own, lease, and operate its properties and
     assets and to carry on its business as it is now being conducted except
     where the failure to have any of such Governmental Authorizations would not
     have a material adverse effect on the business, operations, properties,
     condition (financial or otherwise), assets or liabilities of the Atmos
     Entities, taken as a whole. Atmos is duly qualified or licensed as a
     foreign corporation to do business, and is in good standing, in each
     jurisdiction in which the character of the property owned, leased, or
     operated by it or the nature of the business conducted by it makes such
     qualification or licensing necessary, except in such jurisdictions (if any)
     where the failure to be duly qualified or licensed does not and would not
     have a material adverse effect on the business, operations, properties,
     condition (financial or otherwise), assets or liabilities of the Atmos
     Entities, taken as a whole.

          (b)  Atmos has not been a subsidiary or division of another corpora-
     tion or entity at any time during the two-year period prior to the date of
     this Agreement.

          (c)  Atmos has heretofore delivered to United Cities true, correct, 
     and complete copies of Atmos' Articles of Incorporation and Bylaws,
     including all amendments thereto.

     Section 2.2  Subsidiaries.
     -----------  ------------ 

          (a)  Atmos does not directly or indirectly own any equity or similar
     interest in any corporation, partnership, joint venture, or other business
     association or entity other than (i) Atmos Energy Services, a Delaware
     corporation that is wholly owned by Atmos, (ii) EGASCO, Inc., a Texas
     corporation that is wholly owned by Atmos, (iii) EnerMart, 

                                       13
<PAGE>
 
     Inc., a Delaware corporation that is wholly owned by Atmos, (iv) EnerMart
     Trust, a Pennsylvania business trust that is wholly owned by EnerMart,
     Inc., (v) Trans Louisiana Industrial Gas Company, Inc., a Louisiana
     corporation that is wholly owned by Atmos, and (vi) Western Kentucky Gas
     Resources Company, a Delaware corporation that is wholly owned by Atmos
     (collectively, the "Atmos Subsidiaries"). (Atmos and the Atmos Subsidiaries
     are referred to collectively in this Agreement as the "Atmos Entities.")
     Atmos is the sole record and beneficial owner of, and has good and valid
     title to, all of the outstanding shares of capital stock of the Atmos
     Subsidiaries other than EnerMart Trust, and EnerMart, Inc. is the sole
     record and beneficial owner of, and has good and valid title to, all of the
     outstanding equity ownership interests in EnerMart Trust, in each case free
     and clear of all liens, mortgages, pledges, security interests or other
     encumbrances. All of the outstanding capital stock of each of the Atmos
     Subsidiaries that is a corporation, and, in the case of EnerMart Trust, the
     equity ownership interest held by EnerMart, Inc., has been duly authorized
     and validly issued, is fully paid and nonassessable.

          (b)  Each of the Atmos Subsidiaries (other than EnerMart Trust) is a
     corporation duly organized, validly existing, and in good standing under
     the laws of the jurisdiction of its incorporation and has all requisite
     corporate power and authority and possesses all Governmental Authorizations
     necessary to own, lease, and operate its properties and assets and to carry
     on its business as it is now being conducted except where the failure to
     have any of such Governmental Authorizations would not have a material
     adverse effect on the business, operations, properties, condition
     (financial or otherwise), assets or liabilities of the Atmos Entities,
     taken as a whole. Each of the Atmos Subsidiaries (other than EnerMart
     Trust) is duly qualified or licensed as a foreign corporation to do
     business, and is in good standing, in each jurisdiction in which the
     character of the property owned, leased, or operated by it or the nature of
     the business conducted by it makes such qualification or licensing
     necessary, except in such jurisdictions (if any) where the failure to be
     duly qualified or licensed does not and would not have a material adverse
     effect on the business, operations, properties, condition (financial or
     otherwise), assets or liabilities of the Atmos Entities, taken as a whole.

          (c)  EnerMart Trust is a business trust duly organized, validly
     existing and in good standing under the laws of the State of Pennsylvania
     and has all requisite business trust power and authority to own, lease, and
     operate its properties and assets and to carry on its business as it is now
     being conducted.

          (d)  Atmos has heretofore delivered to United Cities true, correct and
     complete copies of the Articles of Incorporation and Bylaws, including all
     amendments thereto, of the Atmos Subsidiaries, and the organizational
     documents of EnerMart Trust.

     Section 2.3  Capitalization.  The entire authorized capital stock of Atmos
     -----------  --------------                                               
consists of 75,000,000 shares of common stock, no par value ("Atmos Stock").  
As of June 30, 1996, (a) 15,982,304 shares of Atmos Stock were issued and 
outstanding, all of which were duly

                                       14
<PAGE>
 
authorized, validly issued, fully paid, and nonassessable and free of preemptive
rights, and (b) no shares of Atmos Stock were held in the treasury of Atmos.
There are no options, warrants, or other rights, agreements, arrangements, or
commitments of any character relating to the issued or unissued capital stock of
the Atmos Entities or obligating the Atmos Entities to issue or sell any shares
of capital stock of, or any securities convertible into or evidencing the right
to purchase any shares of capital stock of or other equity interests in, the
Atmos Entities. There are no obligations, contingent or otherwise, of the Atmos
Entities to repurchase, redeem, or otherwise acquire any shares of capital stock
or other equity interests in any of the Atmos Entities.

     Section 2.4  Authority Relative to this Agreement.  Atmos has all requisite
     -----------  ------------------------------------                          
corporate power and authority to execute and deliver this Agreement and to
perform its obligations hereunder and to consummate the transactions
contemplated hereby, subject to the approval of Atmos shareholders as
contemplated in this Agreement and the terms and conditions of this Agreement.
The execution and delivery of this Agreement by Atmos and the consummation by
Atmos of the transactions contemplated hereby have been duly and validly
authorized by Atmos' Board of Directors and, except for the approval of the
shareholders of Atmos, no other corporate proceedings on the part of Atmos are
necessary to authorize this Agreement or to consummate the transactions so
contemplated. This Agreement has been duly and validly executed and delivered by
Atmos and constitutes the legal, valid, and binding obligation of Atmos and is
enforceable against Atmos in accordance with its terms, subject to bankruptcy,
insolvency, moratorium and other laws generally affecting creditors' rights.

     Section 2.5  No Conflict; Required Filings and Consents.  The execution,
     -----------  ------------------------------------------                 
delivery, and performance of this Agreement by Atmos and the consummation by
Atmos of the transactions contemplated hereby in accordance with the terms and
conditions hereof, including the Merger, do not and will not:

          (a)  conflict with the Articles of Incorporation or Bylaws of the 
     Atmos Entities or, in the case of EnerMart Trust, its organizational 
     documents;

          (b)  conflict with or violate any law, rule, regulation, order,
     judgment, or decree applicable to any of the Atmos Entities or by which any
     of them or any of their respective properties is bound or affected;

          (c)  except for those consents and waivers required to be obtained
     pursuant to Section 4.6, require from any person other than a governmental
     or regulatory authority any consent, approval, or notice under, or violate,
     result in any breach of, constitute a default (or an event that with notice
     or lapse of time or both would become a default) under, or give to others
     any rights of termination, amendment, acceleration, or cancellation of, or
     result in the creation of a lien or encumbrance on any of the property or
     assets of any of the Atmos Entities pursuant to, any note, bond, mortgage,
     indenture, contract, agreement, lease, license, or other instrument or
     obligation to which any of the 

                                       15
<PAGE>
 
     Atmos Entities is a party or by which any of the Atmos Entities or any of
     their respective properties is bound or affected; or

          (d)  require any consent, approval, authorization, or permit of, or
     filing with or notification to, any governmental or regulatory authority
     except (i) the applicable  requirements of federal and state securities
     laws, (ii) the filing requirements under the Hart-Scott-Rodino Act, (iii)
     the filing and recordation of appropriate merger or other documents as
     required by the Texas Business Corporation Act, the Illinois Business
     Corporation Act, and the Virginia Stock Corporation Act, (iv) approvals of
     the applicable state public utility commissions in the states in which
     Atmos or United Cities is doing business, and (v) approval of the Federal
     Energy Regulatory Commission.

     Section 2.6  Compliance.  None of the Atmos Entities is in breach, default,
     -----------  ----------                                                    
or violation of, and no event has occurred or is occurring that with notice or
lapse of time or both would become a breach, default, or violation of, (a) any
of the Atmos Entities' Articles of Incorporation or Bylaws, or, in the case of
EnerMart Trust, its organizational documents, (b) any law, rule, regulation,
order, judgment, or decree applicable to any of the Atmos Entities or by which
any of them or any of their respective properties is bound or affected, or (c)
any note, bond, mortgage, indenture, contract, agreement, lease, license,
permit, franchise, or other instrument or obligation to which any of the Atmos
Entities is a party or by which any of them or any of their respective
properties is bound or affected, nor have any of them received and not finally
resolved any complaint, citation, or notice of a breach, default, or violation
of any of the foregoing nor are any threatened.

     Section 2.7  Environmental Matters.
     -----------  --------------------- 

          (a)  No Hazardous Materials are now located in, on, at, upon, or under
     the Subject Property currently owned or operated by any of the Atmos
     Entities or have migrated or emanated, or threaten to migrate or emanate,
     to adjacent property in a quantity or manner that is required to be
     reported under any Environmental Requirements, or that is in violation of
     any Environmental Requirements, or for which any of the Atmos Entities will
     be liable under any Environmental Requirements for the cost of remediation
     or other response if such costs are incurred by an Environmental Agency;
     and no Hazardous Materials have been located in, on, at, upon, or under the
     Subject Property, or migrated or emanated from the Subject Property at any
     time prior to or during the Use of the Subject Property by any of the Atmos
     Entities in a quantity or manner that is required to be reported under any
     Environmental Requirements, or that is in violation of any Environmental
     Requirements, or for which any of the Atmos Entities will be liable under
     any Environmental Requirements for the cost of remediation or other
     response if such costs are incurred by an Environmental Agency.

          (b)  No Hazardous Materials have been generated, stored, transported,
     disposed of on-site, or sent off-site from, in, on, at, or upon the Subject
     Property at any time during 

                                       16
<PAGE>
 
     the Use of the Subject Property by any of the Atmos Entities (or prior to
     the Use of the Subject Property by any of the Atmos Entities) in a quantity
     or manner that is required to be reported under any Environmental
     Requirements, or that is in violation of any Environmental Requirements, or
     for which any of the Atmos Entities will be liable under any Environmental
     Requirements for the cost of remediation or other response if such costs
     are incurred by an Environmental Agency.

          (c)  There are no off-site locations where Hazardous Materials
     generated or transported from the Subject Property have been stored,
     treated, recycled, or disposed of by any of the Atmos Entities or their
     agents, employees, or representatives in a quantity or manner that is
     required to be reported under any Environmental Requirements, or that is in
     violation of any Environmental Requirements, or for which any of the Atmos
     Entities will be liable under any Environmental Requirements for the cost
     of remediation or other response if such costs are incurred by an
     Environmental Agency.

          (d)  Each of the Atmos Entities has all permits, licenses, or
     authorizations from any  Environmental Agency that it is required to have
     by any Environmental Requirement in order to operate any aspect of the
     Subject Property currently operated by it or the business currently
     conducted at the Subject Property; the Use of the Subject Property
     currently Used by each of the Atmos Entities, including but not limited to
     any and all Environmental Activity, and all Environmental Conditions, is
     and has been in compliance with all Environmental Requirements during the
     Use of the Subject Property by each of the Atmos Entities and at all times
     prior to its Use by each of the Atmos Entities.

          (e)  No Environmental Costs have been suffered by any of the Atmos
     Entities or by any third party prior to or during the Use of the Subject
     Property by any of the Atmos Entities, and Atmos is not aware of, and has
     not received notice of, any past or present events, conditions,
     circumstances, activities, practices, incidents, actions, or plans that may
     result in Environmental Costs or that may give rise to any common law or
     legal liability based on or related to the manufacture, processing,
     distribution, use, treatment, storage, disposal, transport, or handling or
     the emission, discharge, release, or threatened release into the
     environment, of any pollutant, contaminant, chemical, or industrial toxic
     or hazardous substance or waste or Hazardous Materials.

          (f)  None of the Atmos Entities has Used, in the past, any facilities
     that could reasonably be expected to subject any of the Atmos Entities to
     Environmental Costs.

          (g)  All of the manufactured gas plants now or formerly Used by any of
     the Atmos Entities and all locations where waste from these plants was
     disposed of are set forth in the Atmos SEC Reports.

          (h)  All of the underground storage tanks located on the Subject
     Property are set forth in the Atmos SEC Reports.

                                       17
<PAGE>
 
     Section 2.8  Contracts.  Atmos has made available to United Cities all
     -----------  ---------                                                
material contracts, loan agreements, indentures, commitments, and other
agreements or documents to which any of the Atmos Entities is a party or by
which any of the Atmos Entities or any of their respective properties is bound
or affected.  All such contracts and instruments are in full force and effect
and no party thereto is in default thereunder and no default is threatened
thereunder.

     Section 2.9  SEC Filings; Financial Statements; Absence of Undisclosed
     -----------  ---------------------------------------------------------
     Liabilities.
     ----------- 

          (a)  Atmos has filed all forms, reports, and documents required to be
     filed with the SEC since January 1, 1993, and has heretofore delivered or
     made available to Atmos, in the form filed with the SEC, (i) its Annual
     Reports on Form 10-K for the fiscal years ended September 30, 1993 through
     1995, (ii) its Quarterly Report on Form 10-Q for the periods ended December
     31, 1995 and March 31, 1996, (iii) all proxy statements relating to Atmos'
     meetings of shareholders (whether annual or special) held since January 1,
     1993, (iv) all Forms 8-K filed by Atmos with the SEC since January 1, 1993,
     (v) all other reports or registration statements filed by Atmos with the
     SEC since January 1, 1993, and (vi) all amendments and supplements to all
     such reports, registration statements and proxy statements filed by Atmos
     with the SEC since January 1, 1993 (collectively, the "Atmos SEC Reports").
     As of their respective dates, the Atmos SEC Reports were prepared in
     substantial compliance with the requirements of the Securities Act  or the
     Exchange Act, as the case may be, and did not at the time they were filed
     contain any untrue statement of a material fact or omit to state a material
     fact required to be stated therein or necessary in order to make the
     statements therein, in the light of the circumstances under which they were
     made, not misleading.  None of the Atmos Entities other than Atmos is
     subject to the reporting requirements of the Exchange Act.

          (b)  Atmos has heretofore delivered or made available to United Cities
     its audited consolidated financial statements for its fiscal years ended
     September 30, 1993 through 1995 and its unaudited consolidated financial
     statements for the periods ended December 31, 1995 and March 31, 1996.  All
     such financial statements of Atmos that have been delivered or made
     available to United Cities have been prepared in accordance with generally
     accepted accounting principles applied (except as otherwise noted therein)
     on a consistent basis throughout the periods covered thereby (subject, in
     the case of any such financial statements that are unaudited, to year-end
     adjustments in such amount and of such type as are or will be consistent
     with adjustments made in prior fiscal years).  The consolidated financial
     statements (together with the related notes thereto) fairly present in all
     material respects the consolidated financial condition and consolidated
     results of operation of Atmos as of and for the respective dates indicated.

          (c)  None of the Atmos Entities has any liabilities or obligations
     (whether accrued, absolute, contingent, known or unknown, or otherwise)
     that (i) are not accrued or reserved against in the consolidated balance
     sheet of Atmos as at March 31, 1996 or reflected in the notes thereto in
     accordance with generally accepted accounting principles 

                                       18
<PAGE>
 
     consistently applied or (ii) were incurred after the date of such balance
     sheet outside of the ordinary course of business of any of the Atmos
     Entities.

     Section 2.10  Books and Records.  Atmos has made available to United
     ------------  -----------------                                     
Cities, and will continue to make available to United Cities, all of the Atmos
Entities' books, records, and certificates.  All of such books, records, and
certificates are true, complete, and correct.

     Section 2.11  Conduct of Business in Ordinary Course; Absence of Certain
     ------------  ----------------------------------------------------------
Changes or Events.  Since March 31, 1996, each of the Atmos Entities has
- -----------------                                                       
conducted its business only in the ordinary course; and, since such date, there
has not been any adverse change in the business, operations, properties,
condition (financial or otherwise), assets or liabilities of the Atmos Entities,
taken as a whole, or any condition, event, or development that will result in an
adverse change in the business, operations, properties, condition (financial or
otherwise), assets or liabilities of the Atmos Entities, taken as a whole.

     Section 2.12  Litigation.  There are no material claims, actions, suits,
     ------------  ----------                                                 
investigations, or proceedings pending or threatened against or affecting any of
the Atmos Entities or any of their respective properties or rights at law or in
equity before or by any court, arbitrator, or administrative, governmental, or
regulatory authority or body.  None of the Atmos Entities nor any of their
respective properties is subject to any order, writ, judgment, injunction,
decree, determination, or award.

     Section 2.13  Title to, and Condition of, Assets.  Each of the Atmos
     ------------  ----------------------------------                    
Entities has good and marketable title to, or a valid leasehold interest in, all
of its assets and properties, real and personal, including the properties,
assets, and leasehold interests reflected in the Atmos balance sheet dated March
31, 1996 referred to in Section 2.9 of this Agreement (except for any properties
or assets disposed of in the ordinary course of business since the date of such
balance sheet), necessary or appropriate for the operation of its business, free
and clear of all liens, mortgages, pledges, security interests, or other
encumbrances (except for matters set forth in the notes to such balance sheet
and the notes to the December 31, 1995 balance sheet).  All of the Atmos
Entities' properties and assets are in good condition and repair (ordinary wear
and tear excepted) and are adequate and sufficient for the conduct of the Atmos
Entities' businesses.

     Section 2.14  Intellectual Property.  The Atmos Entities own or possess, or
     ------------  ---------------------                                        
can acquire on reasonable terms, the patents, patent rights, licenses,
inventions, copyrights, know-how (including trade secrets and other unpatentable
proprietary or confidential information, systems or procedures), trademarks,
service marks and trade names presently employed by them in connection with the
business now operated by them, and none of the Atmos Entities has received any
notice of infringement of or conflict with asserted rights of others with
respect to any of the foregoing which, singly or in the aggregate, if the
subject of an unfavorable decision, ruling or finding, would result in any
material adverse change in the business, operations, properties, condition
(financial or otherwise), assets or liabilities, of the Atmos Entities, taken as
a whole.

                                       19
<PAGE>
 
     Section 2.15  Taxes.  All Tax Returns of or relating to any Taxes that are
     ------------  -----                                                       
required to be filed with respect to Atmos and the Atmos Subsidiaries or any of
their income, properties, or operations have been duly filed on a timely basis
and were true, complete, and correct.  All Taxes attributable to Atmos and the
Atmos Subsidiaries or any of their income, properties, or operations that are or
were due and payable have been timely paid, and Atmos and the Atmos Subsidiaries
have no liability for any Taxes other than with respect to their current taxable
year for which adequate provisions have been made and are reflected in Atmos'
consolidated financial statements in accordance with generally accepted
accounting principles.

     Section 2.16  Employee Benefit Plans.
     ------------  ---------------------- 

          (a)  Atmos has previously delivered or made available to United Cities
     true, correct and complete copies of (i) each Plan that is a "multiemployer
     plan," as defined in ERISA Section 4001, (ii) each other employee benefit
     plan as defined in Section 3(3) of ERISA with respect to which an Atmos
     Entity or any Group Member is a "Party in Interest," as defined in Section
     3(14) of ERISA, and (iii) each other Employee Benefit Arrangement.

          (b)  Each Atmos Entity, each Group Member, and each Plan is now, and
     has been from its inception, in compliance with the provisions of ERISA and
     the Code insofar as ERISA and the Code are applicable to such Plans.  Each
     Plan intended to be qualified under Section 401(a) of the Code has been
     determined to be so qualified by the IRS and nothing has occurred since the
     date of the last such determination which resulted or is likely to result
     in the revocation of such determination.  All required reports and
     descriptions of each Plan have been timely filed and distributed as
     required by ERISA.

          (c)  There has not occurred with respect to any Plan any non-exempt
     "Prohibited Transaction," as defined in either Section 406 of ERISA or
     Section 4975 of the Code.

          (d)  There has not occurred with respect to any Plan any "Reportable
     Event," as defined in Section 4043 of ERISA.  No Plan has applied for or
     obtained a waiver from the IRS of any minimum funding requirement under
     Section 412 of the Code.

          (e)  (i) No Plan has been terminated, and no withdrawal from any
     "multiemployer plan," as defined in Section 4001 of ERISA, has occurred
     since the inception of any Plan under circumstances that have given rise
     to, or would give rise to, any actual or potential liability to the PBGC or
     any other person (excluding liabilities to participants (other than any
     liability for unpaid benefits) for benefits payable in the normal course of
     events pursuant to any such termination or withdrawal), (ii) no event or
     condition exists which presents a risk of termination of any Plan by the
     PBGC, and (iii) there is no actual or potential liability to the PBGC or
     any other person expected by the Atmos Entities or any Group Member to be
     incurred with respect to any Plan, including, but not limited to, any
     liability for premium payments, for any accumulated funding 

                                       20
<PAGE>
 
     deficiency as defined in Section 302 of ERISA or for any minimum funding
     contribution under Section 302 of ERISA.

          (f)  The current value (as defined in Section 4062(b)(1)(A) of ERISA)
     of all accrued  benefits (as defined in Section 3 of ERISA) under each Plan
     which is a plan subject to the provisions of Title IV of ERISA does not, as
     of the date of the most recent actuarial report for such Plan exceed the
     current value of the assets of such Plan allocable to such accrued
     benefits, except with respect to the Greeley Gas Company Employees' Pension
     Plan.

          (g)  No lien imposed under Section 412(n) of the Code exists in favor
     of any Plan upon any property belonging to a Group Member.

          (h)  Atmos has previously delivered or made available to United Cities
     true, correct and complete copies of the annual reports and actuarial
     reports for the preceding two plan years (1993 and 1994) filed with respect
     to each such Plan and Employee Benefit Arrangement, summary plan
     descriptions and other communications to employees relating to each such
     Plan and Employee Benefit Arrangement, any related trust or third-party
     funding vehicle documents and related financial statements, and all letters
     from the IRS, if any, confirming the tax-exempt status or qualification
     under Section 401(a) of the Code of any Plan.  There are no Plans or
     Employee Benefit Arrangements other than those previously delivered and
     made available to United Cities.

          (i)  Neither (i) the Atmos Entities, or any director, officer,
     employee, or agent of an Atmos Entity, has, with respect to any Plan, nor
     (ii) any Plan or trust created thereunder or trustee or administrator
     thereof has, engaged in any conduct that would result in any penalties
     under Section 502(i) of ERISA or any liability under Section 409 of ERISA
     for breach of fiduciary duty.  No civil or criminal action or claim (other
     than uncontested claims for benefits) is pending or threatened with respect
     to any Plan.

          (j)  None of the Atmos Entities, any Group Member, or any director,
     officer, or employee of any of the foregoing have taken any elective action
     that would commit an Atmos Entity to continue any Plan or Employee Benefit
     Arrangement or any benefit thereunder for any present or former employee of
     an Atmos Entity or that would prevent such Atmos Entity from changing or
     terminating any such benefit or plan; provided, that this representation
     shall not be construed to apply with respect to any express provision of a
     document which provides for such effect without further action or election
     by such persons.

          (k)  No Atmos Entity now has in effect, or previously had in effect,
     any welfare benefit plan, commitment, understanding, or arrangement
     providing for medical or death benefits (whether insured or uninsured) with
     respect to current or former employees beyond their date of retirement or
     other termination of service (other than coverage 

                                       21
<PAGE>
 
     mandated by Section 4980B of the Code and Section 601 of ERISA, the cost of
     which is fully paid by the former employee or his or her dependents),
     except as otherwise provided under the Atmos Energy Corporation Retiree
     Medical Plan.

          (l)  For purposes of this Section 2.16, the terms "Employee Benefit
     Arrangement," "Group Member" and "Plan" shall be interpreted to exclude all
     reference to United Cities Entities under Section 8.1(l), (v) and (hh)
     hereof.

     Section 2.17  Labor Matters.   Atmos has no labor contracts or collective
     ------------  -------------                                              
bargaining agreements.  There are no employee activities or controversies
(including, but not limited to, any labor organizing activities, election
petitions or proceedings preparatory thereto, unfair labor practice complaints,
labor strikes, disputes, slowdowns, or work stoppages) pending or, to Atmos'
knowledge, threatened, between any of the Atmos Entities and any of their
employees.

     Section 2.18  Disclosure; Information in the Proxy Statement/Prospectus.
     ------------  ---------------------------------------------------------  
No representation or warranty by Atmos in this Agreement and no statement
contained in any certificate furnished or to be furnished by Atmos to United
Cities pursuant to the provisions of this Agreement contains or will contain any
untrue statement of material fact or omits or will omit to state any material
fact necessary, in light of the circumstances under which it is made, in order
to make the statements herein or therein not misleading.  Any written
information supplied by Atmos specifically for inclusion or incorporation by
reference in the Proxy Statement/Prospectus and which is included or
incorporated by reference therein shall not, at the date the Proxy
Statement/Prospectus (or any amendment thereof or supplement thereto) is filed
with the SEC, at the time of the Atmos Shareholders Meeting, at the time of the
United Cities Shareholders Meeting, and at the time the Proxy
Statement/Prospectus becomes effective with the SEC as a registration statement,
be false or misleading with respect to any material fact, omit to state any
material fact required to be stated therein or necessary in order to make the
statements made therein, in the light of the circumstances under which they are
made, not misleading, or omit to state any material fact necessary to correct
any statement in any earlier communication with respect to the solicitation of
proxies for the Atmos Shareholders Meeting or the United Cities Shareholders
Meeting that has become materially false or misleading. If at any time prior to
the Effective Time any event relating to any of the Atmos Entities or any of
their respective directors or officers should be discovered by Atmos which
should be set forth in a supplement to the Proxy Statement/Prospectus, Atmos
shall promptly inform United Cities in writing. Notwithstanding the foregoing,
Atmos makes no representation or warranty with respect to any information to be
contained in the Proxy Statement/Prospectus and provided in writing by United
Cities specifically for inclusion or incorporation by reference in the Proxy
Statement/Prospectus.

     Section 2.19  Insurance.  Atmos has not failed to give any notice or
     ------------  ---------                                             
present any claim under any insurance policies or binders maintained by any of
the Atmos Entities with respect to their properties and business in due and
timely fashion.  None of the Atmos Entities has received notice of cancellation
or nonrenewal of any such policy or binder.

                                       22
<PAGE>
 
     Section 2.20  Broker's Fees.  No broker, finder, or investment banker
     ------------  -------------                                          
(other than Merrill Lynch, Pierce, Fenner & Smith Incorporated) is entitled to
any brokerage, finder's, or other fee or commission in connection with the
transactions contemplated by this Agreement based upon arrangements made by or
on behalf of any of the Atmos Entities.

     Section 2.21  No Atmos Investment in United Cities Stock.  None of the
     ------------  ------------------------------------------              
Atmos Entities  has acquired or is the beneficial owner of any United Cities
Stock.

     Section 2.22  Board Recommendation.  The Board of Directors of Atmos has,
     ------------  --------------------                                       
by resolutions duly adopted by the requisite vote of directors present at a
meeting of such Board duly called and held on July 19, 1996, determined that the
Merger in accordance with the terms of this Agreement and the Plan of Merger is
fair and in the best interests of its shareholders and has recommended that the
shareholders of Atmos approve the Merger and Plan of Merger, and ratify this
Agreement.

     Section 2.23  PUHCA.   Neither Atmos nor any other of the Atmos Entities is
     ------------  -----                                                        
required to register under PUHCA, or the rules and regulations thereunder.

     Section 2.24  Regulation as a Utility.  Atmos is a regulated public utility
     ------------  -----------------------                                      
in the States of Texas, Louisiana, Kentucky, Colorado, Missouri and Kansas and
in no other state.  Neither Atmos nor any Atmos Entity is subject to regulation
as a public utility or public service company (or similar designation) by any
other state in the United States, by the United States or any agency or
instrumentality of the United States or by any foreign country.

     Section 2.25  Vote Required.  The approval of the Merger by holders of two-
     ------------  -------------                                               
thirds of the shares of outstanding Atmos Stock is the only vote of the holders
of any class or series of the capital stock of Atmos required to approve this
Agreement, the Plan of Merger, the Merger, and the other transactions
contemplated hereby.

     Section 2.26  Opinion of Financial Advisor.  Atmos has received the opinion
     ------------  ----------------------------                                 
of Merrill Lynch, Pierce, Fenner & Smith Incorporated, dated the date hereof, to
the effect that, as of the date hereof, the exchange ratio set forth in the Plan
of Merger is fair from a financial point of view to the holders of Atmos Stock.

                                   ARTICLE 3

                           COVENANTS OF UNITED CITIES

     Section 3.1  Conduct of Business by United Cities Pending the Merger.
     -----------  -------------------------------------------------------  
United Cities covenants and agrees that, between the date of  this Agreement and
the Effective Time, unless Atmos shall otherwise agree in writing, each of the
United Cities Entities shall conduct its business only in the ordinary course of
business and in a manner consistent with past practice; and United Cities shall
use its best efforts to maintain the corporate existence of each of the United

                                       23
<PAGE>
 
Cities Entities and preserve substantially intact the business and organization
of each of the United Cities Entities, to keep available the services of its
present officers, employees, and consultants, and to preserve the relationships
and goodwill of each of the United Cities Entities with its customers,
suppliers, and other persons with which it has significant business relations.
By way of amplification but not limitation, United Cities shall not and shall
not permit any of the United Cities Subsidiaries, between the date of this
Agreement and the Effective Time, directly or indirectly, to do, agree to do, or
propose to do any of the following without the prior written consent of Atmos:

          (a)  amend or otherwise change its Articles of Incorporation, Bylaws,
     Certificate of Formation or Limited Liability Company Agreement;

          (b)  issue, sell, pledge, dispose of, or encumber, or authorize the
     issuance, sale, pledge, disposition, or encumbrance of, (i) any shares of
     capital stock of any class, or any options, warrants, convertible
     securities, or other rights of any kind to acquire any shares of capital
     stock, or any other ownership interest, of any of the United Cities
     Entities (other than in the ordinary course of business pursuant to United
     Cities' Long-Term Stock Plan of 1989, Non-Employee Director Stock Plan,
     Employee Stock Purchase Plan, Customer Stock Purchase Plan, Dividend
     Reinvestment and Stock Purchase Plan, and 401(k) Savings Plan), except that
     United Cities may issue shares of its common stock upon the exercise or
     conversion in accordance with their terms of any options, warrants,
     convertible securities or other rights to acquire such stock that were
     outstanding on the date of this Agreement and disclosed in the United
     Cities Disclosure Schedule or (ii) any assets of any of the United Cities
     Entities (except for sales of assets in the ordinary course of business and
     in a manner consistent with past practice);

          (c)  declare, set aside, make, or pay any dividend or other
     distribution, payable in cash, stock, property, or otherwise, with respect
     to any of its capital stock, except for regular quarterly cash dividends
     declared and paid by United Cities in a manner and amount consistent with
     past practice, and dividends declared and paid by the United Cities
     Subsidiaries;

          (d)  reclassify, combine, split, subdivide or redeem, purchase, or
     otherwise acquire or offer to acquire, directly or indirectly, any of its
     capital stock;

          (e)  acquire (by merger, consolidation, or acquisition of stock or
     assets) any corporation, partnership, or other business organization or
     division thereof, except for acquisitions, the fair market value of the
     consideration for which exceeds $3,000,000 individually or $10,000,000 in
     the aggregate, or acquire any shares of Atmos Stock;

          (f)  incur any indebtedness for borrowed money or issue any debt
     securities or assume, guarantee, or endorse, or otherwise as an
     accommodation become responsible for, the obligations of any person, or
     make any loans or advances (except for indebtedness 

                                       24
<PAGE>
 
     incurred under existing lines of credit in the ordinary course of business
     consistent with past practice and except for indebtedness issued under
     United Cities' currently effective shelf registration statement in a
     principal amount not to exceed $15,000,000 in the aggregate), or mortgage,
     pledge or subject to any lien or other encumbrance any assets of any of the
     United Cities Entities;

          (g)  enter into or amend any contract, agreement, commitment, or
     arrangement other than in the ordinary course of business;

          (h)  authorize any capital expenditures that are in excess of (i)
     $500,000  for any single project and (ii) $30,000,000 in the aggregate
     since July 1, 1996;

          (i)  increase the compensation payable or to become payable to its
     officers or employees, except for increases in salary or wages of non-
     officer employees of the United Cities Entities in accordance with past
     practices or grant any severance or termination pay or stock options to, or
     enter into any employment or severance agreement with any director,
     officer, or other employee of any of the United Cities Entities, or
     establish, adopt,  enter into, or amend any collective bargaining, bonus,
     profit sharing, thrift, compensation, stock option, restricted stock,
     pension, retirement, deferred compensation, employment, termination,
     severance, or other plan, agreement, trust, fund, policy, or arrangement
     for the benefit of any current or former directors, officers, or employees;

          (j)  make any loan or advance (except for normal business expense
     advances) to any of the United Cities Entities' directors, officers,
     employees, or shareholders (of United Cities), or to any other person or
     entity or cancel without payment in full any note, loan, or other
     obligation receivable from any director, officer, employee, or shareholder
     of any of the United Cities Entities or any member of their families or
     from any corporation or other entity in which any director, officer,
     employee, or shareholder or any member of their families has any direct or
     indirect interest known to United Cities;

          (k)  take any action other than in the ordinary course of business and
     in a manner consistent with past practice (none of which actions shall be
     unreasonable or unusual) with respect to accounting policies or procedures
     (including, without limitation, procedures with respect to the payment of
     accounts payable and collection of accounts receivable);

          (l)  make any tax election or settle or compromise any material
     federal, state, local, or foreign income tax liability or settle, waive, or
     compromise any other material claim, including litigation;

          (m)  pay, discharge, or satisfy any claims, liabilities, or obliga-
     tions (absolute, accrued, asserted or unasserted, contingent or otherwise),
     other than as may be paid, 

                                       25
<PAGE>
 
     discharged, or satisfied in the ordinary course of business and consistent
     with past practice;

          (n)  take any action or omit to take any necessary action, which 
     action or omission results in any breach of or constitutes a default (or an
     event that with notice or lapse of time or both would become a default)
     under any material note, bond, mortgage, indenture, contract, agreement,
     lease, license, permit, franchise, or other instrument or obligation to
     which any of the United Cities Entities is a party or by which any of the
     United Cities Entities or any of their respective properties is bound or
     affected; or

          (o)  cause any circumstance that might result in a Material adverse
     change in the business, operations, properties, condition (financial or
     otherwise), assets or liabilities of the United Cities Entities, taken as a
     whole.

     Section 3.2  No Solicitation of Competing Transaction.  Subject to the
     -----------  ----------------------------------------                 
provisions of Section 3.11 below, United Cities agrees that it shall (a) not,
and that it shall not permit any of the United Cities Subsidiaries or any of its
or their respective officers, directors, employees, agents and representatives
(including, without limitation, any investment banker, attorney or accountant)
to, initiate, solicit or encourage (including by way of furnishing information
or assistance), or take any other action to facilitate, any inquiries
concerning, or the making or implementation of, any proposal relating to, or
that may reasonably be expected to lead to any Competing Transaction, or engage
in any negotiations concerning, agree to or endorse, provide any confidential
information or data to, or have any discussions with, any person relating to, a
Competing Transaction; and (b) notify Atmos promptly if any such inquiries or
proposals are received by, any such information is requested from, or any such
negotiations or discussions are sought to be initiated or continued with, United
Cities or any of the United Cities Subsidiaries, or any of its or their
officers, directors, employees, agents and representatives (such notification to
include the terms of the inquiry or proposal, the identity of the parties making
such inquiry or proposal and, if such inquiry or proposal is in writing, a copy
of the inquiry or proposal).

     Section 3.3  Access to Information.  From the date hereof to the Effective
     -----------  ---------------------                                        
Time,  United Cities will, and will cause its directors, officers, employees,
and agents to, permit and afford Atmos and its representatives full and complete
access at all reasonable times to the employees, offices, properties, books, and
records of the United Cities Entities, including the audit work papers of, and
all correspondence with, its certified public accountants, and will furnish
Atmos with all financial, operating, and other data and information as Atmos,
through its officers, employees, or representatives, may reasonably request.

     Section 3.4  Environmental Audit and Covenants.
     -----------  --------------------------------- 

          (a)  Upon execution of this Agreement, United Cities and Atmos shall
     cooperate to provide such information, files and documents as United Cities
     and Atmos shall reasonably request of the other party concerning the
     Environmental Activities and 

                                       26
<PAGE>
 
     Environmental Condition of the respective parties. Within sixty (60) days
     ("Initial Environmental Inspection Period") after the date of this
     Agreement, United Cities and Atmos shall meet and mutually agree upon a
     site assessment and environmental compliance audit of the Subject Property
     currently Used by each of the United Cities Entities and any Subject
     Property formerly Used by any of the United Cities Entities and described
     in the United Cities Disclosure Schedule pursuant to Section 1.7(f), which
     assessment and audit shall be in scope, form, and substance ("Scope"), and
     prepared by an independent, competent, and qualified engineer, reasonably
     satisfactory to United Cities and to Atmos (the "Environmental Audit").
     United Cities shall not withhold its agreement to a Scope that does not
     involve any invasive or subsurface testing, provided that such Scope is
     reasonable based upon the information obtained during the Initial
     Environmental Inspection Period. The terms of the engagement of the
     engineer shall be approved by United Cities and Atmos. The engagement
     agreement shall provide that the Environmental Audit shall be issued to
     United Cities and Atmos and that United Cities and Atmos shall have all of
     the same rights as United Cities under the engagement agreement. Any
     investigation conducted by Atmos prior to the earlier of the expiration of
     the Initial Environmental Inspection Period or the agreement upon the Scope
     will be at the expense of Atmos. Within ninety (90) days ("Additional
     Environmental Investigation Period") of the end of the Initial
     Environmental Inspection Period, United Cities shall cause to be prepared
     and submit to Atmos the Environmental Audit at the sole cost and expense of
     the United Cities Entities.

          (b)  In the event that United Cities and Atmos cannot agree upon a
     Scope for the Environmental Audit, then Atmos, at its sole discretion, may
     during the Initial Environmental Inspection Period, commission at its sole
     cost and expense such additional investigation and assessment work as Atmos
     determines is reasonable, but which United Cities does not approve
     ("Additional Assessment"), and this Additional Assessment will be part of
     the Scope; provided, however, in no event shall surface or subsurface soil
     or groundwater sampling or assessment ("Sampling") of a Subject Property
     previously or currently held as a manufacturing gas plant be a part of the
     Scope. The United Cities Entities will pay the agreed upon portions of the
     Scope and Atmos will pay the costs of the Additional Assessment. United
     Cities agrees to permit Atmos to enter upon the Subject Property within
     United Cities' control to perform the Additional Assessment, provided,
     however, that United Cities shall have the right, and Atmos' permission to
     enter is so limited, to refuse to permit Atmos to enter upon any Subject
     Property previously or currently held as a manufactured gas plant to
     perform Additional Assessment work that involves Sampling.

          (c)  The Environmental Audit shall include a "Disclosure Summary" that
     specifically addresses any exceptions to the representations and warranties
     set forth in Section 1.7 of this Agreement and shall include a "Conclusion"
     section that states whether there is a low, medium, or high probability of
     environmental impairment or liability associated with a Subject Property,
     whether the current operations of each United Cities 

                                       27
<PAGE>
 
     Entity at a Subject Property are in compliance with Environmental
     Requirements, and whether further investigation is recommended. If further
     investigation is recommended by the initial Environmental Audit, the scope
     and extent of this investigation and the engineer performing the
     investigation must be mutually approved by United Cities and Atmos. All
     costs of the further investigation shall be paid by United Cities. Except
     in connection with the right to refuse access to any Subject Property
     previously used as a manufactured gas plant, the agreement of United Cities
     to any additional investigation will not be unreasonably withheld.

          (d)  United Cities further agrees that prior to Closing it shall:

               (i)    comply with all applicable Environmental Requirements
          relating to the Subject Property currently Used by United Cities and
          the Use of such Subject  Property by United Cities, and not engage in
          or permit others to engage in any Environmental Activity in violation
          of any applicable Environmental Requirements;

               (ii)   deliver to Atmos no later than three (3) days following 
          the occurrence of any such event, written notice of the discovery by
          United Cities of any event, the occurrence of which would render any
          representation or warranty contained in Section 1.7 of this Agreement
          incorrect in any material respect if made at the time of such
          discovery; and

               (iii)   cause any party who Uses the Subject Property currently
          Used by United Cities to comply with this Section 3.4(d).

     Section 3.5  Consents and Approvals.
     -----------  ---------------------- 

          (a)  United Cities shall use all reasonable efforts to obtain all
     consents, waivers, approvals, authorizations, and orders of all third
     parties and local, state, and federal governmental authorities (including,
     but not limited to, the approvals of the Iowa Utility Board, Kansas
     Corporation Commission, Missouri Public Service Commission, Illinois
     Commerce Commission, Tennessee Regulatory Authority, Georgia Public Service
     Commission, South Carolina Public Service Commission, Virginia State
     Corporation Commission and the Federal Energy Regulatory Commission
     required in connection with the authorization, execution, and delivery of
     this Agreement and the consummation of the transactions contemplated
     hereby.  United Cities shall attend all proceedings of, and file all
     documents with, the Iowa Utility Board, Kansas Corporation Commission,
     Missouri Public Service Commission, Illinois Commerce Commission, Tennessee
     Regulatory Authority, Georgia Public Service Commission, South Carolina
     Public Service Commission, Virginia State Corporation Commission and the
     Federal Energy Regulatory Commission that are necessary to obtain each of
     such commissions' approval of the Merger.  United Cities shall also
     cooperate with and assist Atmos in all proceedings before 

                                       28
<PAGE>
 
     and in the preparation and filing of any documents it is required to file
     with the Colorado Public Utilities Commission, Kansas Corporation
     Commission, Kentucky Public Service Commission, and Missouri Public Service
     Commission, and with respect to the preparation of the Proxy
     Statement/Prospectus and Listing Application to the NYSE.

          (b)  United Cities shall, as soon as practicable after the date of 
     this Agreement, file any Notification and Report Forms and related material
     that it may be required to file with the Federal Trade Commission and the
     Antitrust Division of the Department of Justice under the Hart-Scott-Rodino
     Act, shall use its reasonable efforts to obtain an early termination of the
     applicable waiting period, and shall make any further filings pursuant
     thereto that may be necessary, proper, or advisable and respond as promptly
     as practicable to all inquiries received from the Federal Trade Commission
     or the Antitrust Division of the Department of Justice for additional
     information or documentation.

          (c)  United Cities shall use all reasonable efforts to arrange for the
     transfer to Atmos on the Closing Date of all permits required by
     Environmental Requirements for the Use of the Subject Property and all
     other permits material to the continued operation of United Cities'
     business.

     Section 3.6  Meeting of United Cities Shareholders.  As soon as practicable
     -----------  -------------------------------------                         
following the approval by the SEC of the Proxy Statement/Prospectus, United
Cities shall take all action necessary in accordance with the Illinois Business
Corporation Act and Virginia Stock Corporation Act and its Articles of
Incorporation and Bylaws to convene a meeting of its shareholders promptly to
consider and vote upon approval of the Merger and the Plan of Merger, and the
ratification of this Agreement. United Cities shall, subject to Section 3.11,
use its reasonable efforts to solicit from the shareholders of United Cities
proxies in favor of such approval and ratification and take all other action
reasonably necessary or, in the reasonable opinion of United Cities, helpful to
secure a vote of the shareholders of United Cities in favor of the Merger and
the Plan of Merger, and the ratification of this Agreement.

     Section 3.7  Shareholder Appraisal Rights.  United Cities shall not settle
     -----------  ----------------------------                                 
or compromise  any claim for shareholder appraisal rights in respect of the
Merger prior to the Effective Time without the prior written consent of Atmos.

     Section 3.8  Insurance.  Through the Effective Time, United Cities shall
     -----------  ---------                                                  
maintain in full force and effect all of the policies of insurance of the United
Cities Entities that were in effect on the date hereof or insurance comparable
to the coverage afforded by such policies.

     Section 3.9  Agreement of Certain United Cities Shareholders Regarding Rule
     -----------  --------------------------------------------------------------
145 Compliance.  At or prior to the Closing Date, United Cities shall deliver to
- --------------                                                                  
Atmos a certificate identifying each of its shareholders who in United Cities'
reasonable judgment is an affiliate of United Cities for purposes of SEC Rule
145 and shall use all reasonable efforts to obtain from such affiliates a
written agreement, in form and substance satisfactory to Atmos, not to offer to

                                       29
<PAGE>
 
sell, sell, or otherwise dispose of any shares of Atmos Stock received in the
Merger (a) except pursuant to an effective registration statement under the
Securities Act or in compliance with SEC Rule 145, as amended from time to time,
or in a transaction which, in the opinion of legal counsel (such opinion and
counsel being reasonably satisfactory to Atmos) is exempt from the registration
requirements of the Securities Act and (b) in no event at any time prior to the
public release and dissemination by Atmos of financial results covering at least
thirty (30) days of the combined operations of Atmos and United Cities.  Such
agreement shall also include the agreement and acknowledgement of each of such
shareholders that his or her shares of Atmos Stock received in the Merger shall
contain a legend setting forth the restrictions that such shares may be sold
only as provided in this Section 3.9.

     Section 3.10  Cooperation in Registration of Atmos Stock.  United Cities
     ------------  ------------------------------------------                
shall cooperate fully with Atmos and shall furnish such information concerning
United Cities as Atmos shall request in connection with the registration with
the SEC by Atmos of the Atmos Stock and the preparation and filing with the SEC
by Atmos of the Proxy Statement/Prospectus in connection with the Atmos
Shareholders Meeting.  In addition, United Cities shall obtain the consent of
Arthur Andersen LLP to the inclusion of such audited financial statements of
United Cities in the Proxy Statement/Prospectus as may be necessary or
desirable, as determined by Atmos.

     Section 3.11  Fiduciary Limitations.
     ------------  --------------------- 

          (a)  Nothing contained in this Agreement, including without limitation
     Sections 3.1, 3.2 and 5.6(b) hereof, shall prohibit United Cities from (i)
     furnishing information to, or entering into discussions or negotiations
     with, any person or entity that makes an unsolicited contact in connection
     with a bona fide Competing Transaction, if, and only to the extent that,

                    (A)  the Board of Directors of United Cities determines in
               good faith, based on, among other matters, the written advice of
               independent legal counsel (which for the purposes of this
               Agreement includes Chapman and Cutler), that such action is
               required for the Board of Directors to comply with its fiduciary
               duties to shareholders imposed by law;

                    (B)  prior to United Cities furnishing any confidential
               information to such other person, such other person executes a
               confidentiality agreement with United Cities in customary form;

                    (C)  prior to furnishing such information to, or entering
               into discussions (other than responding to an initial inquiry) or
               negotiations with, such person or entity, United Cities provides
               written notice to Atmos to the effect that it is furnishing
               information to, or entering into discussions or negotiations
               with, such person or entity; and

                                       30
<PAGE>
 
                    (D)  United Cities keeps Atmos reasonably informed of the
               status of any such discussions or negotiations; or

(ii)  taking or disclosing to the shareholders of United Cities a position with
respect to any such  Competing Transaction, or the Merger that, in the judgment
of the Board of Directors of United Cities, as determined in good faith based
on, among other matters, the written advice of independent legal counsel, is
required for the Board of Directors to comply with its fiduciary duties to
shareholders imposed by law, and, to the extent applicable, complying with Rule
14e-2 promulgated under the Exchange Act with regard to a Competing Transaction.

          (b)  Nothing in this Section 3.11 shall (i) permit United Cities to
     terminate this Agreement (except as specifically provided in Section 7.1
     hereof), or (ii) permit United Cities to enter into any agreement with
     respect to a Competing Transaction during the term of this Agreement (it
     being agreed that during the term of this
     Agreement, United Cities shall not enter into any agreement with any person
     that provides for, or in any way facilitates, a Competing Transaction
     (other than a confidentiality agreement in customary form)).

     Section 3.12  Delivery of Monthly Financials.  United Cities shall deliver
     ------------  ------------------------------                              
to Atmos, as promptly as practicable following the end of each calendar month
after the date of this Agreement, its consolidated monthly financial statements
prepared in the ordinary course of its business.

     Section 3.13  Termination of Supplemental Executive Retirement Plan.  Prior
     ------------  -----------------------------------------------------        
to Closing, United Cities shall have (a) terminated the United Cities and
Subsidiaries Supplemental Executive Retirement Plan and all accompanying Joinder
Agreements, (b) obtained waivers and releases from all "active participants" (as
defined in such Plan), with respect to any and all rights and benefits to which
they were entitled thereunder and (c) in order to cover all obligations
currently in pay status under such Plan, purchased an annuity for Mr. Bobby
Gaylor (in an amount equal to the most favorable commercial rate available from
an "excellent" rated insurance company) and, in consideration therefor, obtained
his release with respect to any further rights and benefits to which he is
entitled under such Plan.  In consideration for such waivers and releases (other
than those obtained from Mr. Gaylor), United Cities shall pay to each such
participant (other than Mr. Gaylor) an amount equal to one dollar less than
three hundred percent (300%) of the average of such participant's compensation
paid by United Cities and included in his or her gross income for Federal income
tax purposes for the five (5)-year period ending on the December 31 immediately
preceding the Closing Date; provided that, the aggregate of all such payments
shall not exceed $5,000,000.  Notwithstanding the preceding provisions of this
Section 3.13, Mr. Gene Koonce shall, prior to the Closing Date, be given the
option to (i) provide a waiver and release with respect to his rights and
benefits under the United Cities Gas and Subsidiaries Supplemental Executive
Retirement Plan, in which event he shall receive payment pursuant to the
immediately preceding sentence of $2,247,434 or (ii) continue to participate in
such Plan.  If Mr. Koonce elects to provide such a waiver, then the aggregate
amount of payments made to all participants shall be increased by the payment
made to Mr. Koonce in consideration for such waiver.

                                       31
<PAGE>
 
     Section 3.14  Directors' and Officers' Insurance.  United Cities shall use
     ------------  ----------------------------------                          
its best efforts to procure a policy of directors' and officers' liability
insurance, to be effective for a period of five (5) years, with respect to
matters involving United Cities and occurring prior to the consummation of the
Merger, and, if United Cities does obtain such a policy, to use its best efforts
to assign the benefits of such policy to Atmos following the consummation of the
Merger.

                                   ARTICLE 4

                               COVENANTS OF ATMOS

          Section 4.1  Conduct of Business by Atmos Pending the Merger.  Atmos
          -----------  -----------------------------------------------        
covenants and agrees that, between the date of this Agreement and the Effective
Time, unless United Cities shall otherwise agree in writing, each of the Atmos
Entities shall conduct its business only in the ordinary course of business and
in a manner consistent with past practice; and Atmos shall use its best efforts
to maintain the corporate existence of each of the Atmos Entities that is a
corporation and preserve substantially intact the business and organization of
each of the Atmos Entities.  Atmos shall not and shall not permit any of the
Atmos Subsidiaries, between the date of this Agreement and the Effective Time,
directly or indirectly, to do, agree to do, or propose to do any of the
following without the prior written consent of United Cities:

          (a)  except as otherwise contemplated by this Agreement, amend or
     otherwise change its Articles of Incorporation or Bylaws;

          (b)  issue, sell, pledge, dispose of, or encumber, or authorize the
     issuance, sale, pledge, disposition, or encumbrance of, (i) any shares of
     capital stock of any class, or any options, warrants, convertible
     securities, or other rights of any kind to acquire any shares of capital
     stock, or any other ownership interest, of any of the Atmos Entities (other
     than in the ordinary course of business pursuant to Atmos' Restricted Stock
     Grant Plan, Dividend Reinvestment and Stock Purchase Plan, Employee Stock
     Ownership Plan and Directors' Stock for Fee Plan), except that Atmos may
     issue shares of its common stock upon the exercise or conversion in
     accordance with their terms of any options, warrants, convertible
     securities or other rights to acquire such stock that were outstanding on
     the date of this Agreement and disclosed in the Atmos Disclosure Schedule
     or (ii) any assets of any of the Atmos Entities (except for sales of assets
     in the ordinary course of business and in a manner consistent with past
     practice);

          (c)  declare, set aside, make, or pay any dividend or other
     distribution, payable in cash, stock, property, or otherwise, with respect
     to any of its capital stock, except for regular quarterly cash dividends
     declared and paid in a manner and amount consistent with past practice;

          (d)  reclassify, combine, split, subdivide or redeem, purchase, or
     otherwise acquire or offer to acquire, directly or indirectly, any of its
     capital stock;

                                       32
<PAGE>
 
          (e) acquire (by merger, consolidation, or acquisition of stock or
     assets) any corporation, partnership, or other business organization or
     division thereof, except

     for acquisitions the consideration for which exceeds $10,000,000
     individually or $20,000,000 in the aggregate, or acquire any shares of
     United Cities Stock;

          (f) make any loan or advance (except for normal business expense
     advances) to any of the Atmos Entities' directors, officers, employees, or
     shareholders (of Atmos), or to any other person or entity or cancel without
     payment in full any note, loan, or other obligation receivable from any
     director, officer, employee, or shareholder of any of the Atmos Entities or
     any member of their families or from any corporation or other entity in
     which any director, officer, employee, or shareholder or any member of
     their families has any direct or indirect interest known to Atmos;

          (g) take any action other than in the ordinary course of business and
     in a manner consistent with past practice (none of which actions shall be
     unreasonable or unusual) with respect to accounting policies or procedures
     (including, without limitation, procedures with respect to the payment of
     accounts payable and collection of accounts receivable);

          (h) take any action or omit to take any necessary action, which action
     or omission results in any breach of or constitutes a default (or an event
     that with notice or lapse of time or both would become a default) under any
     material note, bond, mortgage, indenture, contract, agreement, lease,
     license, permit, franchise, or other instrument or obligation to which any
     of the Atmos Entities is a party or by which any of the Atmos Entities or
     any of their respective properties is bound or affected; or

          (i) cause any circumstance that might result in a Material adverse
     change in the business, operations, properties, condition (financial or
     otherwise), assets or liabilities of the Atmos Entities, taken as a whole.

     Section 4.2  Meeting of Atmos Shareholders.  As soon as practicable
     -----------  -----------------------------                         
following the approval by the SEC of the Proxy  Statement/Prospectus, Atmos
shall take all action necessary in accordance with the Texas Business
Corporation Act and its Articles of Incorporation and Bylaws to convene a
meeting of its shareholders promptly to consider and vote upon approval of the
Merger and the Plan of Merger, the ratification of this Agreement, and the
approval of the issuance of the Atmos Stock to the United Cities shareholders.
Atmos will use its reasonable efforts to solicit from the shareholders of Atmos
proxies in favor of such approvals and ratification and will take all other
action reasonably necessary or, in the reasonable opinion of Atmos, helpful to
secure a vote of the shareholders of Atmos in favor of the Merger and the Plan
of Merger, the ratification of this Agreement, and the issuance of Atmos Stock
contemplated hereby and thereby.

     Section 4.3  Registration and Listing of Atmos Stock.  As soon as
     -----------  ---------------------------------------             
practicable after the date of this Agreement, Atmos will file a registration
statement on Form S-4 with the

                                      33
<PAGE>
 
SEC under the Securities Act with respect to the offering, sale, and delivery of
the shares of Atmos Stock to be issued to United Cities' shareholders pursuant
to this Agreement and the Plan of Merger; and Atmos will use all reasonable
efforts to cause such registration statement to become effective as promptly as
practicable after filing and to cause the shares of Atmos Stock registered
thereby to be duly listed for trading on the NYSE.  Atmos shall also use all
reasonable efforts to take any action required to be taken under state
securities laws with respect to the Atmos Stock.

     Section 4.4  Access to Information.  From the date hereof to the Effective
     -----------  ---------------------                                        
Time,  Atmos will, and will cause its directors, officers, employees, and agents
to, permit and afford United Cities and its representatives full and complete
access at all reasonable times to the employees, offices, properties, books, and
records of the Atmos Entities, including the audit work papers of, and all
correspondence with, its certified public accountants, and will furnish United
Cities with all financial, operating, and other data and information as United
Cities, through its officers, employees, or representatives, may reasonably
request.

     Section 4.5  Environmental Covenants.  Atmos agrees that prior to Closing
     -----------  -----------------------                                     
it shall:

          (a) comply with all applicable Environmental Requirements relating to
     the Subject Property currently Used by Atmos and the Use of such Subject
     Property by Atmos, and not engage in or permit others to engage in any
     Environmental Activity in violation of any applicable Environmental
     Requirements;

          (b) deliver to United Cities no later than three (3) days following
     the occurrence of any such event, written notice of the discovery by Atmos
     of any event, the occurrence of which would render any representation or
     warranty contained in Section 2.7 of this Agreement incorrect in any
     material respect if made at the time of such discovery; and

          (c) cause any party who Uses the Subject Property currently Used by
     Atmos to comply with this Section 4.5.

     Section 4.6  Consents and Approvals.
     -----------  ---------------------- 

          (a) Atmos shall use all reasonable efforts to obtain all consents,
     waivers, approvals, authorizations, and orders of all third parties and
     local, state, and federal governmental authorities (including, but not
     limited to, the approvals of the Colorado Public Utilities Commission,
     Kansas Corporation Commission, Kentucky Public Service Commission, and
     Missouri Public Service Commission) required in connection with the
     authorization, execution, and delivery of this Agreement and the
     consummation of the transactions contemplated hereby.  Atmos shall attend
     all proceedings of, and file all documents with, the Colorado Public
     Utilities Commission, Kansas Corporation Commission, Kentucky Public
     Service Commission, and Missouri

                                      34

<PAGE>
 
     Public Service Commission that are necessary to obtain each of such
     commissions' approval of the Merger.  Atmos shall also cooperate with and
     assist United Cities in all proceedings before and in the preparation and
     filing of any documents it is required to file with the Iowa Utility Board,
     Kansas Corporation Commission, Missouri Public Service Commission, Illinois
     Commerce Commission, Tennessee Regulatory Authority, Georgia Public Service
     Commission, South Carolina Public Service Commission, Virginia State
     Corporation Commission and the Federal Energy Regulatory Commission.

          (b) Atmos shall, as soon as practicable after the date of this
     Agreement, file any Notification and Report Forms and related material that
     it may be required to file with the Federal Trade Commission and the
     Antitrust Division of the Department of Justice under the Hart-Scott-Rodino
     Act, shall use its reasonable efforts to obtain an early termination of the
     applicable waiting period, and shall make any further filings pursuant
     thereto that may be necessary, proper, or advisable and respond as promptly
     as practicable to all inquiries received from the Federal Trade Commission
     or the Antitrust Division of the Department of Justice for additional
     information or documentation.

     Section 4.7  Employees and Employee Benefits.
     -----------  ------------------------------- 

          (a) At the Effective Time, all employees of the United Cities Entities
     shall become employees of Atmos.  Such employees' titles and job duties
     will be determined by Atmos in its sole discretion.  Except as otherwise
     set forth in Section 4.7(b) hereof, Atmos agrees to retain all of such
     employees for a period of one (1) year following the Effective Time at
     their approved rate of pay as in effect immediately prior to such Effective
     Time; provided, however, that Atmos shall have the right to terminate any
     such employee for cause; provided, further, that no such employee who is a
     former officer of any of the United Cities Entities shall be terminated for
     cause during such one (1)-year period without having been given a
     reasonable opportunity to cure and correct, to the satisfaction of Atmos,
     the deficiencies or other circumstances giving rise to such cause.
     Following such one (1)-year period, such employees will be employed by
     Atmos on an "at will" basis.

          (b) At the Closing, Atmos will enter into an employment contract with
     each of Messrs. James B. Ford and Thomas R. Blose, Jr. for a term of three
     (3) years, which contracts shall be in substantially the forms of Exhibits
     C-1 and C-2, respectively,  to this Agreement.  In addition, at the
     Closing, Atmos will enter into an employment contract with Mr. Gene C.
     Koonce for a term of six (6) months, which contract shall be in
     substantially the form of Exhibit C-3 to this Agreement.

          (c) During the one (1)-year period described in Section 4.7(a) hereof
     and except as otherwise provided in Section 3.13 hereof, any employee of a
     United Cities

                                      35

<PAGE>
 
     Entity who continues his or her employment with Atmos as set forth in such
     Section 4.7(a) and who was a participant in a Plan or Employee Benefit
     Arrangement maintained by a United Cities Entity shall continue to
     participate in such Plan or Employee Benefit Arrangement which shall be
     maintained by Atmos during such one (1)-year period; provided, however,
     that, during such period, Atmos shall have the right to merge or terminate
     any such Plan or Employee Benefit Arrangement if, in its sole judgment,
     Atmos determines that the same or better benefits are available to the
     employees covered thereunder under a Plan or Employee Benefit Arrangement
     which provides the same or similar benefits, which was maintained by Atmos
     before the Effective Time (and continues to be so maintained) and under
     which immediate coverage for such employees can be provided.  Atmos will
     credit all employees of the United Cities Entities who continue their
     employment with Atmos as set forth in Section 4.7(a) and (b) above for
     service performed as employees of the United Cities Entities prior to the
     Effective Time for eligibility, participation and vesting (but not benefit
     accrual) purposes in any employee plan or program maintained by Atmos at or
     after the Effective Time for which such employees are eligible (it being
     understood that employees who continue to be covered under any Plan or
     Employee Benefit Arrangement previously maintained by any United Cities
     Entity will not, during the period of such coverage,  be eligible to
     participate in any Plan or Employee Benefit Arrangement which provides the
     same or similar benefits and which was maintained by Atmos before the
     Effective Time).  Certain key management employees as selected by Atmos
     will be eligible to participate in Atmos' Annual Performance Bonus Plan for
     Key Management Employees and Atmos' Mini-Med Plan.  Subject to the
     foregoing, the rights of any employees of the United Cities Entities at or
     after the Effective Time shall be governed by the terms, as may be amended
     or modified from time to time, of any Atmos Plan or Employee Benefit
     Arrangement in which they participate.  Those employees of the United
     Cities Entities, if any, who become participants in one of Atmos' defined
     benefit pension plans will have no rights in or claims against Atmos'
     pension or retirement funds, except with respect to contributions made for
     their benefit subsequent to the Effective Time.

          (d) It is expressly understood by the parties hereto that, except as
     otherwise provided in Section 4.7(c) hereof, Atmos assumes no
     responsibility, and makes no commitment, for the maintenance and
     continuation, after the Closing, of any Plan or Employee Benefit
     Arrangement previously adopted or maintained by any United Cities Entity or
     any United Cities Group Member, provided that a decision to discontinue any
     such Plan or Employee Benefit Arrangement shall not be based solely on the
     status of the participants thereunder as former employees of the United
     Cities Entities.

          (e) Atmos shall provide coverage for each individual (other than Mr.
     Gene Koonce) who was an active participant in the United Cities Gas and
     Subsidiaries

                                      36

<PAGE>
 
     Supplemental Executive Retirement Plan immediately prior to the date on
     which this Agreement was signed, under a "death benefit only" plan
     providing the same "survivor benefit" as provided under, and defined in,
     Section 4.4 of the United Cities and Subsidiaries Supplemental Executive
     Retirement Plan; provided that United Cities shall have, prior to the
     Effective Time, transferred ownership of any and all insurance policies
     described in Section 7.12(b) of such Plan to Atmos.

     Section 4.8  Declaration of Dividends.  Atmos will take appropriate action,
     -----------  ------------------------                                      
at the first regularly scheduled meeting of Atmos'  Board of Directors after the
Effective Time, to cause to be declared and paid, for a period of not less than
four (4) quarters, quarterly cash dividends at an indicated annual rate of not
less than $1.02 per share (subject to adjustment for any stock split, stock
dividend, combination of shares or other similar event), except to the extent
that the ability of Atmos' Board of  Directors to declare, and Atmos' ability to
pay, such dividends are limited by applicable state statutory requirements of
the state or states in which Atmos is incorporated or by such directors'
fiduciary duties to Atmos and its shareholders, as such fiduciary duties are
determined by Atmos and its counsel in their sole discretion.

     Section 4.9  Options.  Following the consummation of the Merger, Atmos
     -----------  -------                                                  
agrees to continue in effect the United Cities Gas Company Long-Term Stock Plan
of 1989, as amended.  Persons holding options under such plan shall be allowed
to exercise their options for Atmos Stock at the exchange rate set forth in the
Plan of Merger.  Persons holding stock appreciation rights under such plan shall
be allowed to exercise such rights based on the price of Atmos Stock taking into
account the exchange rate set forth in the Plan of Merger.

     Section 4.10  Indemnification.  Atmos agrees that all rights to
     ------------  ---------------                                  
indemnification and advancement of expenses existing in favor of the present or
former directors, officers, employees, fiduciaries and agents of the United
Cities Entities (collectively, the "Indemnified Parties") as provided in United
Cities' Articles of Incorporation or Bylaws as in effect as of the date hereof
with respect to matters occurring prior to the Effective Time shall survive the
Merger and shall continue in full force and effect for a period of not less than
the statutes of limitations applicable to such matters.

     Section 4.11  Insurance.  Through the Effective Time, Atmos shall maintain
     ------------  ---------                                                   
in full force and effect all of the policies of insurance of the Atmos Entities
that were in effect on the date hereof or insurance comparable to the coverage
afforded by such policies.

     Section 4.12  Cooperation in Preparation of Proxy Statement/Prospectus.
     ------------  --------------------------------------------------------  
Atmos shall cooperate fully with United Cities and shall furnish such
information concerning Atmos as United Cities shall request in connection with
the preparation and filing with the SEC by United Cities of the Proxy
Statement/Prospectus in connection with the United Cities Shareholders Meeting.
In addition, Atmos shall obtain the consent of Ernst & Young LLP

                                      37
<PAGE>
 
to the inclusion of such audited financial statements of Atmos in the Proxy
Statement/Prospectus as may be necessary or desirable, as determined by Atmos.

     Section 4.13  Delivery of Monthly Financials.  Atmos shall deliver to
     ------------  ------------------------------                         
United Cities, as promptly as practicable following the end of each calendar
month after the date of this Agreement, its consolidated monthly financial
statements prepared in the ordinary course of its business.

                                   ARTICLE 5

                  MUTUAL COVENANTS OF ATMOS AND UNITED CITIES

     Section 5.1  The Merger.
     -----------  ---------- 

          (a) Subject to the terms and conditions of this Agreement, Atmos and
     United Cities agree to enter into a statutory merger under the applicable
     laws of the States of Texas, Illinois and Virginia whereby United Cities
     will be merged with and into Atmos, with Atmos as the surviving corporation
     (the "Merger"); and Atmos and United Cities hereby respectively agree that
     the terms and conditions of such Merger, the mode of carrying the same into
     effect, the manner of converting the shares of capital stock of United
     Cities into shares of Atmos Stock, and other necessary or proper details
     and provisions relating to such Merger shall be as contained in the form of
     Plan of Merger attached hereto as Exhibit D (the "Plan of Merger").
     Notwithstanding anything to the contrary contained in this Agreement or the
     Plan of Merger, if any state authority or commission requires that the
     survivor pursuant to the Merger be a corporation incorporated under the
     laws of such state, each party agrees to take all necessary actions prior
     to the mailing of the Proxy Statement/Prospectus to comply with such
     requirement and provide that such survivor will be incorporated in such
     state, including, without limitation, making any necessary amendments to
     the Plan of Merger, as authorized by the respective Board of Directors of
     United Cities and Atmos by approval of this Agreement.

          (b) At any time before approval of this Agreement and the Plan of
     Merger by the respective shareholders of Atmos and United Cities and prior
     to the Closing Date, this Agreement and the Plan of Merger may be amended
     in writing by Atmos and United Cities in accordance with the provisions of
     Section 7.3.

          (c) The closing of the transactions contemplated hereby (the
     "Closing") shall take place at 10:00 a.m., local time, within fifteen (15)
     business days following the latest to occur of (i) the meeting of
     shareholders of Atmos held pursuant to Section 4.2 of this Agreement, (ii)
     the meeting of shareholders of United Cities held pursuant to Section 3.6
     of this Agreement, (iii) the expiration or termination of the waiting
     period (and any extension thereof) applicable to the consummation of the

                                      38

<PAGE>
 
     Merger under the Hart-Scott-Rodino Act, or (iv) the date all approvals
     contemplated by Section 6.1(c) of this Agreement have been granted, and
     each of the other conditions set forth in Article VI hereof have been
     satisfied, or at such other date and time as Atmos and United Cities shall
     agree upon in writing (the "Closing Date").  The Closing shall take place
     at the office of Locke Purnell Rain Harrell (A Professional Corporation) at
     2200 Ross Avenue, Suite 2200, Dallas, Texas 75201 or at such other place as
     Atmos and United Cities shall agree upon in writing.

          (d) The "Paying Agent" referred to in the Plan of Merger shall be
     Boston EquiServe Limited Partnership or such other party as Atmos and
     United Cities may mutually agree.

     Section 5.2  Execution, Filing, and Recording of Merger Documents.  Subject
     -----------  ----------------------------------------------------          
to the terms and conditions of this Agreement and upon approval and adoption of
the Plan of Merger by the respective shareholders of United Cities and Atmos in
accordance with the laws of Texas, Illinois and Virginia, as applicable,
relating to statutory mergers, Atmos and United Cities each agree to properly
execute and deliver the Plan of Merger in compliance with the laws of Texas,
Illinois and Virginia, as well as the requisite certificate(s) and articles of
merger in compliance with the laws of Texas, Illinois and Virginia, as
applicable, and to cause the requisite filing and recording of the
certificate(s) and articles of merger in accordance with the laws of the States
of Texas, Illinois and Virginia, as applicable, all with a view of making the
Merger effective at the Closing Date.

     Section 5.3  Notice of Certain Events.  Each of the parties hereto shall
     -----------  ------------------------                                   
give prompt written notice to the other party of (a) the occurrence, or non-
occurrence, of any event, the occurrence or non-occurrence of which would be
likely to cause any representation or warranty of such party contained in this
Agreement to be untrue or inaccurate and (b) any failure of such party to comply
with or satisfy any cost, condition, or agreement to be complied with or
satisfied by it hereunder; provided, however, that the delivery of any notice
pursuant to this Section 5.3 shall not limit or otherwise affect the remedies
available hereunder to the other party hereto.

     Section 5.4  Expenses.  Except as otherwise provided in this Section 5.4,
     -----------  --------                                                    
all costs and expenses incurred in connection with this Agreement, the Plan of
Merger, and the transactions contemplated hereby and thereby (including without
limitation any fees, commissions or expenses of the type referred to in Sections
1.20 and 2.20 above) shall be paid by the party incurring such expense.  The SEC
filing fee for registering the Atmos Stock on Form S-4 and the expenses incurred
in connection with printing and mailing the Proxy Statement/Prospectus shall be
shared equally by Atmos and United Cities.  Notwithstanding the foregoing, if

                                      39

<PAGE>
 
          (a)  this Agreement is terminated

               (i) by United Cities, because of the failure of Atmos to satisfy
          the conditions to closing set forth in Sections 6.1(a), 6.3(a),
          6.3(b), or 6.3(c) or the failure of Atmos to obtain the opinion
          described in Section 6.2(d) hereof; or

               (ii) by Atmos, because of the failure of United Cities to satisfy
          the conditions to closing set forth in Sections 6.1(a), 6.2(a),
          6.2(b), 6.2(c), or 6.2(g) or the failure of United Cities to obtain
          the opinion described in Section 6.3(d) hereof,

then the terminating party shall be reimbursed, by the party failing to satisfy
such condition(s), for its reasonable expenses (including attorneys, accountants
and investment bankers fees (as accrued as of the date of termination)) incurred
in connection with this Agreement and the transactions contemplated hereby; and

          (b) if this Agreement is terminated by United Cities under Section
     7.1(k), by Atmos under Section 7.1(c), or by Atmos because United Cities'
     shareholders have approved a Competing Transaction involving United Cities,
     then United Cities will pay to Atmos a fee in immediately available funds
     equal to $15,000,000 promptly, but in no event later than two (2) business
     days, after such termination.

     Section 5.5  Public Announcements.  Atmos and United Cities shall consult
     -----------  --------------------                                        
with one another before issuing any press release or otherwise making any public
statements with respect to the Merger and shall not issue any such press release
or make any such public statement prior to such consultation, except as may be
required by law, under Atmos'  listing agreement with the NYSE or under United
Cities' listing agreement with Nasdaq.

     Section 5.6  Further Action.  Upon the terms and subject to the conditions
     -----------  --------------                                               
hereof, each of the parties hereto shall (a) promptly make its respective
filings, and thereafter make any other required submissions, and (b) use all
reasonable efforts to take, or cause to be taken, all appropriate action, and to
do or cause to be done, all things necessary, proper, or advisable under
applicable laws and regulations to consummate and make effective the
transactions contemplated by this Agreement and the Plan of Merger, including,
without limitation, using all reasonable efforts to obtain all Governmental
Authorizations and all consents of parties to contracts with Atmos and United
Cities as are necessary for the consummation of the transactions contemplated by
this Agreement and the Plan of Merger and to fulfill the conditions of the
Merger.  In case at any time after the Effective Time any further action is
necessary or desirable to carry out the purposes of this Agreement, the parties
to this Agreement shall use all reasonable efforts to take all such necessary
action.

                                      40

<PAGE>
 
 
                                 ARTICLE 6

                    CONDITIONS TO CONSUMMATION OF THE MERGER

          Section 6.1  Conditions to Obligations of Each Party to Effect the
          -----------  -----------------------------------------------------
Merger.  The  respective obligations of each party to  effect the Merger shall
- ------                                                                        
be subject to the satisfaction at or prior to the Closing Date of the following
conditions:

          (a) Shareholder Approvals.  The issuance of the Atmos Stock to the
              ---------------------                                         
     shareholders of United Cities shall have been approved by the requisite
     vote of the shareholders of Atmos as required by the rules of the NYSE, and
     the Merger shall have been approved by the requisite vote of the
     shareholders of Atmos in accordance with the provisions of the Texas
     Business Corporation Act and by the requisite vote of the shareholders of
     United Cities in accordance with the provisions of the Illinois Business
     Corporation Act, the Virginia Stock Corporation Act and Nasdaq.

          (b) Securities Act Registration, Blue Sky Registration or Exemption
              ---------------------------------------------------------------
     and NYSE Listing.  The shares of Atmos Stock to be issued to United Cities'
     ----------------                          
     shareholders pursuant to this Agreement and the Plan of Merger shall have
     been registered with the SEC under the Securities Act by means of an
     effective registration statement, shall have been registered under or shall
     be exempt from registration under all applicable state securities or blue
     sky laws, and shall have been approved for listing, upon official notice of
     issuance, on the NYSE.

          (c) Utility Commission Approvals.  All necessary approvals of the
              ----------------------------                                 
     state public utility commissions for which approval is required shall have
     been granted by final order and all applicable appeal and waiting periods
     shall have expired and such orders shall not contain any condition which,
     in the reasonable judgment of Atmos, would result in a material adverse
     change in the business, operations, properties, condition (financial or
     otherwise), assets or liabilities of the United Cities Entities, taken as a
     whole, or the Atmos Entities, taken as a whole.

          (d) Hart-Scott-Rodino Act.  The waiting period (and any extension
              ---------------------                                        
     thereof) applicable to the consummation of the Merger under the Hart-Scott-
     Rodino Act shall have expired or been terminated.

          (e) Consents Obtained.  All consents and waivers required to be
              -----------------                                          
     obtained for the authorization, execution, and delivery of this Agreement
     and the consummation of the transactions contemplated hereby other than
     those consents and waivers the failure of which to obtain would not have a
     material adverse effect on Atmos or United Cities, as the case may be,
     shall have been obtained, including required consents, waivers and releases
     from each of Atmos' and United Cities' lenders and creditors and from
     Woodward Marketing, L.L.C., in form and substance reasonably satisfactory
     to Atmos and United Cities.

                                      41
<PAGE>
 
          (f) Litigation.  No action, suit, or proceeding shall be pending or
              ----------                                                     
     threatened before any court or quasi-judicial or administrative agency of
     any federal, state, local, or foreign jurisdiction or before any arbitrator
     wherein an unfavorable injunction, judgment, order, decree, ruling, or
     charge would (i) prevent consummation of any of the transactions
     contemplated by this Agreement, (ii) cause any of the transactions
     contemplated by this Agreement to be rescinded following consummation,
     (iii) materially affect adversely the right of Atmos to own the former
     assets and to operate the former business of United Cities and the United
     Cities Subsidiaries, or (iv) materially affect adversely the right of any
     of the United Cities Entities to own its assets and to operate its business
     (and no such injunction, judgment, order, decree, ruling, or charge shall
     be in effect).

          (g) Pooling Letter.  Atmos shall have received from Ernst & Young LLP
              --------------                                                   
     a written opinion dated the Closing Date, in form and substance
     satisfactory to Atmos, to the effect that pooling of interests accounting
     treatment by Atmos is required for the Merger.

          (h)   Comfort Letters.
                --------------- 

               (i) Immediately prior to the time that the Registration Statement
          on Form S-4 becomes effective, Atmos and United Cities shall have
          received from Ernst & Young LLP a letter dated such date, in form and
          substance satisfactory to Atmos.

               (ii) Immediately prior to the time that the Registration
          Statement on Form S-4 becomes effective, Atmos and United Cities shall
          have received from Arthur Andersen  LLP a letter dated such date, in
          form and substance satisfactory to Atmos.

               (iii)  Atmos and United Cities shall have received from Ernst &
          Young LLP a letter, dated as of the Closing Date, to the effect that
          they reaffirm the statements made in the letter furnished pursuant to
          subsection (i) of this Section 6.1(h), except that the specified date
          referred to shall be a date not more than five (5) days prior to the
          Closing Date.

               (iv) Atmos and United Cities shall have received from Arthur
          Andersen LLP a letter, dated as of the Closing Date, to the effect
          that they reaffirm the statements made in the letter furnished
          pursuant to subsection (ii) of this Section 6.1(h), except that  the
          specified date referred to shall be a date not more than five (5) days
          prior to the Closing Date.

     Section 6.2  Additional Conditions to Obligations of Atmos.  The
     -----------  ---------------------------------------------      
obligations of Atmos to issue the Atmos Stock to United Cities' shareholders and
to effect the Merger are,

                                      42
<PAGE>
 
at the option of Atmos, also subject to the satisfaction at or prior to the
Closing Date of the following conditions:

          (a) Representations and Warranties.  (i) The representations and
              ------------------------------                              
     warranties of United Cities contained in Sections 1.1, 1.2, 1.3, 1.4,
     1.5(a), 1.5(b), 1.5(d), 1.6(a), 1.6(b), 1.9(a) (except with respect to the
     second sentence of Section 1.9(a) as it relates to financial statements),
     1.10, 1.14, 1.17, 1.18, 1.21, 1.22, 1.23, 1.24, 1.25 and 1.26 of this
     Agreement shall be true and correct in all material respects as of the date
     of this Agreement and as of the Closing Date with the same force and effect
     as if made at and as of the Closing Date, and (ii) all of the other
     representations and warranties of United Cities contained in this Agreement
     shall be true and correct as of the date of this Agreement and as of the
     Closing Date with the same force and effect as if made at and as of the
     Closing Date, except where the failure of such representation(s) or
     warranty(ies) to be true and correct and would not have a Material (as
     defined in Section 8.1(bb)) adverse effect on the United Cities Entities,
     taken as a whole.  Atmos shall have received a certificate signed by the
     Chief Executive Officer and the Chief Financial Officer of United Cities
     dated as of the Closing Date to the foregoing effect.

          (b) Agreements and Covenants.  United Cities shall have performed or
              ------------------------                                        
     complied in all material respects with all agreements and covenants
     required by this Agreement to be performed or complied with by it at or
     prior to the Closing Date and Atmos shall have received a certificate
     signed by the Chief Executive Officer of United Cities and dated as of the
     Closing Date to that effect.

          (c) Material Adverse Changes.  Since the date of this Agreement, no
              ------------------------                                       
     Material adverse change in the business, operations, properties, condition
     (financial or otherwise), assets or liabilities of any of the United Cities
     Entities shall have occurred; and Atmos shall not have discovered or become
     aware of any fact, error, misstatement or omission materially adverse to
     the business, operations, properties, condition (financial or otherwise),
     assets or liabilities of any of the United Cities Entities that has not
     been disclosed by United Cities to Atmos in the United Cities Disclosure
     Schedule which would result in a Material adverse change.

          (d) Opinion of Investment Banker.  The Board of Directors of Atmos
              ----------------------------                                  
     shall have received from Merrill Lynch, Pierce, Fenner & Smith Incorporated
     a written opinion, dated as of the mailing date of the Proxy
     Statement/Prospectus, in form and substance satisfactory to Atmos, to the
     effect that the Merger is fair to the shareholders of Atmos from a
     financial point of view.

          (e) Opinion of Tax Counsel.  Atmos shall have received from Locke
              ----------------------                                       
     Purnell Rain Harrell (A Professional Corporation) a written opinion dated
     the Closing Date, in form and substance satisfactory to Atmos, to the
     effect that the

                                      43

<PAGE>
 
     Merger will constitute a tax-free reorganization pursuant to Section
     368(a)(1)(A) of the Code.

          (f) Opinion of United Cities' Counsel.  Atmos shall have received an
              ---------------------------------                               
     opinion of Chapman and Cutler, counsel to United Cities, dated the Closing
     Date, regarding the United Cities Entities and the Merger, in form and
     substance satisfactory to Atmos.

          (g) Dissenting United Cities Shareholders.  Written objections to the
              -------------------------------------                            
     Merger shall not  have been made by the holders of ten (10%) percent or
     more of the outstanding shares of the common stock of United Cities,
     pursuant to the provisions of the Illinois Business Corporation Act or the
     Virginia Stock Corporation Act, respecting rights of dissenting
     shareholders.

     Section 6.3  Additional Conditions to Obligations of United Cities.  The
     -----------  -----------------------------------------------------      
obligations of United Cities to effect the Merger are, at the option of United
Cities, also subject to the satisfaction at or prior to the Closing Date of the
following conditions:

          (a) Representations and Warranties.  (i) The representations and
              ------------------------------                              
     warranties of Atmos contained in Sections 2.1, 2.2, 2.3, 2.4, 2.5(a),
     2.5(b), 2.5(d), 2.6(a), 2.6(b), 2.9(a) (except with respect to the second
     sentence of Section 2.9(a) as it relates to financial statements), 2.10,
     2.14, 2.17, 2.18, 2.21, 2.22, 2.23, 2.24, 2.25 and 2.26 of this Agreement
     shall be true and correct in all material respects as of the date of this
     Agreement and as of the Closing Date, with the same force and effect as if
     made on and as of the Closing Date, and (ii) all of the other
     representations and warranties of Atmos contained in this Agreement shall
     be true and correct as of the date of this Agreement and as of the Closing
     Date with the same force and effect as if made at and as of the Closing
     Date, except where the failure of such representation(s) and warranty(ies)
     to be true and correct would not have a Material (as defined in Section
     8.1(cc)) adverse effect on the Atmos Entities taken as a whole.  United
     Cities shall have received a certificate signed by the Chief Operating
     Officer and Chief Financial Officer of Atmos dated as of Closing Date to
     the foregoing effect.

          (b) Agreements and Covenants.  Atmos shall have performed or complied
              ------------------------                                         
     in all material respects with all agreements and covenants required by this
     Agreement to be performed or complied with by it at or prior to the Closing
     Date and United Cities shall have received a certificate signed by the
     Chief Operating Officer of Atmos and dated as of the Closing Date to that
     effect.

          (c) Material Adverse Changes.  Since the date of this Agreement, no
              ------------------------                                       
     Material adverse change in the business, operations, properties, condition
     (financial or otherwise), assets or liabilities of any of the Atmos
     Entities shall have occurred;

                                      44
<PAGE>
 
     and United Cities shall not have discovered or become aware of any fact,
     error, misstatement or omission materially adverse to the business,
     operations, properties, condition (financial or otherwise), assets or
     liabilities of any of the Atmos Entities that has not been disclosed by
     Atmos to United Cities in the Atmos Disclosure Schedule which would result
     in a Material adverse change.

          (d) Opinion of Investment Banker.  The Board of Directors of United
              ----------------------------                                   
     Cities shall have received from PaineWebber Incorporated a written opinion,
     dated as of the mailing date of the Proxy Statement/Prospectus, in form and
     substance satisfactory to United Cities, to the effect that the Merger is
     fair to the shareholders of United Cities from a financial point of view.

          (e) Opinion of Tax Counsel.  United Cities shall have received from
              ----------------------                                         
     Chapman and Cutler a written opinion dated the Closing Date, in form and
     substance satisfactory to United Cities, to the effect that the Merger will
     constitute a tax-free reorganization pursuant to Section 368(a)(1)(A) of
     the Code.

          (f) Opinion of Atmos' Counsel.  United Cities shall have received from
              -------------------------                                         
     Locke Purnell Rain Harrell (A Professional Corporation) a written opinion
     dated the Closing Date regarding the Atmos Entities and the Merger, in form
     and substance satisfactory to United Cities.

          (g) Employment Agreements.  Atmos shall have executed employment
              ---------------------                                       
     contracts with Messrs. James B. Ford, Thomas R. Blose, Jr. and Gene C.
     Koonce substantially in the forms of Exhibits C-1, C-2 and C-3,
     respectively.

                                   ARTICLE 7

                       TERMINATION, AMENDMENT, AND WAIVER

     Section 7.1  Termination.  This Agreement may be terminated and the Merger
     -----------  -----------                                                  
contemplated hereby may be abandoned at any time  prior to the Effective Time,
notwithstanding approval thereof by the shareholders of Atmos or United Cities:

          (a) by mutual written consent duly authorized by the Boards of
     Directors of Atmos and United Cities;

          (b) by Atmos or United Cities if the Merger shall not have been
     consummated on or before March 31, 1997, or such later date as may be
     agreed to in writing by the parties; provided, however, that the right to
     terminate this Agreement under this Section 7.1(b) shall not be available
     to any party whose willful failure to fulfill any material obligation under
     this Agreement has been the cause of, or resulted in, the failure of the
     Effective Time to occur on or before such date;

                                      45

<PAGE>
 
     (c) by Atmos if the Board of Directors of United Cities has, pursuant to
     Section 3.11, taken a position recommending a Competing Transaction, or
     whereby it fails to recommend the Merger, to the shareholders of United
     Cities;

          (d) by Atmos or United Cities if a federal or state court of competent
     jurisdiction or a federal or state governmental regulatory or
     administrative agency or commission shall have issued an order, decree or
     ruling or taken any other action permanently restraining, enjoining or
     otherwise prohibiting the transactions contemplated by this Agreement, and
     such order, decree or ruling or other action shall have become final and
     nonappealable; provided, that the party seeking to terminate this Agreement
     pursuant to this Section 7.1(d) shall have used all reasonable efforts to
     remove such injunction, order or decree;

          (e) by Atmos if the shareholders of United Cities have not approved
     the matters specified in Section 3.6 hereof at the vote taken thereon at
     the meeting of shareholders of United Cities convened pursuant to Section
     3.6 hereof or any adjournment thereof;

          (f) by United Cities if the shareholders of Atmos have not approved
     the matters specified in Section 4.2 hereof at the vote taken thereon at
     the meeting of shareholders of Atmos convened pursuant to Section 4.2
     hereof or any adjournment thereof;

          (g) by Atmos if there has occurred (i) a material breach by United
     Cities of any of its representations or warranties contained in Sections
     1.1, 1.2, 1.3, 1.4, 1.5(a), 1.5(b), 1.5(d), 1.6(a), 1.6(b), 1.9(a) (except
     with respect to the second sentence of Section 1.9(a) as it relates to
     financial statements), 1.10, 1.14, 1.17, 1.18, 1.21, 1.22, 1.23, 1.24, 1.25
     or 1.26 of this Agreement or of any of the covenants or agreements,
     contained in this Agreement or the Plan of Merger, or (ii) a Material (as
     defined in Section 8.1(bb)) breach by United Cities of any of its other
     representations or warranties contained in this Agreement or the Plan of
     Merger, if the same has not been cured within twenty (20) days after
     written notice of such breach has been given to United Cities by Atmos;

          (h) by United Cities if there has occurred (i) a material breach by
     Atmos of any of its representations or warranties contained in Sections
     2.1, 2.2, 2.3, 2.4, 2.5(a), 2.5(b), 2.5(d), 2.6(a), 2.6(b), 2.9(a) (except
     with respect to the second sentence of Section 2.9(a) as it relates to
     financial statements), 2.10, 2.14, 2.17, 2.18, 2.21, 2.22, 2.23, 2.24, 2.25
     and 2.26 of this Agreement or any of the covenants or agreements contained
     in this Agreement or the Plan of Merger or (ii) a Material (as defined in
     Section 8.1(cc)) breach by Atmos of any of its other representations or
     warranties contained in this Agreement or the Plan of Merger, if the same
     has not been cured

                                      46

<PAGE>
 
     within twenty (20) days after written notice of such breach has been given
     to Atmos to United Cities;

          (i) by Atmos, prior to the expiration of the Initial Environmental
     Inspection Period, in its sole discretion, because of (i) the failure of
     United Cities and Atmos to agree upon a Scope for the Environmental Audit,
     or (ii) the results of the preliminary review of information about the
     Environmental Activities or Environmental Condition of United Cities are
     not satisfactory to Atmos;

          (j) by Atmos, prior to the expiration of twenty (20) days from and
     after a period of forty (40) days from the date of this Agreement, in its
     sole discretion, in the event United Cities fails to terminate all
     liabilities of United Cities under the United Cities and Subsidiaries
     Supplemental Executive Retirement Plan for an aggregate amount of not more
     than $5,000,000; provided, however, that United Cities shall not be
     required to include in such amount any amount in respect to United Cities'
     liability to Gene C. Koonce under the United Cities and Subsidiaries
     Supplemental Executive Retirement Plan; or

          (k) by United Cities, in the exercise of United Cities' Board of
     Directors' fiduciary duties pursuant to Section 3.11 with respect to a
     Competing Transaction.

     Section 7.2  Effect of Termination.  In the event of the termination of
     -----------  ---------------------                                     
this Agreement pursuant to Section 7.1, except as otherwise expressly provided
for in this Section 7.2, this Agreement shall forthwith become void and, except
as otherwise expressly provided for in this Section 7.2, there shall be no
liability on the part of any party hereto, provided, however, that nothing
herein shall relieve any party from liability for any intentional or willful
breach hereof, provided, further, that the obligations of the parties under
Section 5.4, the Confidentiality Agreement and the Standstill Agreement shall
remain in full force and effect.

     Section 7.3  Amendment.  This Agreement may be amended by mutual action
     -----------  ---------                                                 
taken by  or on behalf of the respective Boards of Directors of the parties
hereto at any time prior to the Closing Date; provided, however, that, after
approval by the shareholders of either party of the Merger, no amendment may be
made which would increase or decrease the amount or change the type of
consideration into which each share of United Cities Stock shall be converted
upon consummation of the Merger, and provided further that any amendments
required by Section 5.1(a) do not require further approval of the respective
Boards of Directors.  This Agreement may not be amended except by an instrument
in writing signed by the parties hereto.

     Section 7.4  Waiver.  At any time prior to the Effective Time, any party
     -----------  ------                                                     
hereto may (a) extend the time for the performance of any of the obligations or
other acts of the other party hereto, (b) waive any inaccuracies in the
representations and warranties contained

                                      47

<PAGE>
 
herein or in any document delivered pursuant hereto, and (c) waive compliance
with any of the agreements or conditions contained herein.  Any such extension
or waiver shall be valid if set forth in an instrument in writing signed by the
party or parties to be bound thereby and shall be applicable only with respect
to the particular condition or provision as extended or waived and not to any
other condition or provision herein.

                                   ARTICLE 8

                                 MISCELLANEOUS

     Section 8.1  Definitions.  For purposes of this Agreement, the following
     -----------  -----------                                                
terms used herein shall have the meanings set forth below:

          (a) "Additional Assessment" has the meaning set forth in Section
     3.4(b) above.

          (b) "Additional Environmental Investigation Period" has the meaning
     set forth in Section 3.4(a) above.

          (c) "Atmos SEC Reports" has the meaning set forth in Section 2.9(a)
     above.

          (d) "Atmos Shareholders Meeting" means the special meeting of Atmos'
     shareholders called for the purpose of considering and voting upon the
     Merger and the issuance of Atmos Stock to United Cities' shareholders as
     consideration for the Merger in accordance with and pursuant to the terms
     and provisions of this Agreement.

          (e) "Atmos Stock" has the meaning set forth in Section 2.3(a) above.

          (f) "Closing" means the closing of the Merger as set forth in Section
     5.1(c) of this Agreement.

          (g) "Closing Date" means the date of the Closing as set forth in
     Section 5.1(c) of this Agreement.

          (h) "Competing Transaction" means any of the following (other than the
     transactions contemplated by this Agreement) involving United Cities or any
     United Cities Entity:  (i) any merger, consolidation, share exchange,
     business combination or similar transaction; (ii) any sale, lease,
     exchange, mortgage, pledge, transfer or other disposition of twenty percent
     (20%) or more of the assets of the United Cities Entities; (iii) any tender
     offer or exchange offer for twenty percent (20%) or more of the outstanding
     shares of capital stock of United Cities; (iv) any person acquiring

                                      48

<PAGE>
 
     beneficial ownership of, or any group (as such term is defined under
     Section 13(d) of the Exchange Act and the rules and regulations promulgated
     thereunder) being formed which beneficially owns or has the right to
     acquire beneficial ownership of, twenty percent (20%) of more of the
     outstanding shares of capital stock of United Cities; or (v) any public
     announcement of a proposal, plan or intention to do any of the foregoing or
     any agreement to engage in any of the foregoing; provided, that this shall
     not apply to transactions permitted under Section 3.1(e).

          (i) "Confidentiality Agreement" means the Confidentiality Agreement
     dated July 5,  1996 by and between United Cities and Atmos .

          (j) "Code" means the Internal Revenue Code of 1986, as amended, and
     regulations promulgated thereunder.

          (k) "Effective Time" means the effective time of the Merger,
     determined in accordance with the Plan of Merger.

          (l) "Employee Benefit Arrangement" means any plan, agreement, or
     arrangement which is not an employee benefit plan within the meaning of
     Section 3(3) of ERISA but which provides benefits to any one or more of the
     officers or other employees of any United Cities Entity or Atmos Entity, as
     the case may be, such as a bonus, incentive, stock purchase, stock option,
     or stock appreciation rights plan, or any employment or consulting
     agreement.

          (m) "Environmental Activity" means any storage, holding, manufacture,
     emission, discharge, generation, processing, treatment, abatement, removal,
     disposition, handling, transportation, or disposal, or any actual,
     proposed, or threatened release of any Hazardous Materials from, under,
     into, or on any Subject Property or otherwise relating to any Subject
     Property or the Use of any Subject Property, including but not limited to
     (i) the migration or emanation of Hazardous Materials from the Subject
     Property onto or into the environment beyond the physical boundaries of the
     Subject Property; (ii) the off-site disposal of Hazardous Materials from
     any Subject Property; and (iii) including but not limited to activity
     occurring in connection with ambient air, surface, and subsurface soil
     conditions, and all surface and subsurface waters.

          (n) "Environmental Agency" means any federal, state, or local entity
     or agency with jurisdiction over Environmental Requirements.

          (o) "Environmental Audit" has the meaning set forth in Section 3.4(a)
     above.

                                      49

<PAGE>

          (p) "Environmental Condition" means (i) the presence or existence in,
     on, at, or under the Subject Property of any Hazardous Materials,
     underground or above-ground storage tanks, wells, covered-over surface
     impoundments or similar areas, any "facility," as that term is defined
     under applicable Environmental Requirements, or wetlands and (ii) the
     presence or existence in, on, at, or under the environment beyond the
     physical boundaries of the Subject Property of any Hazardous Materials,
     which migrated or emanated from the Subject Property.

          (q) "Environmental Costs" means any of the following which arise in
     any manner in connection with Environmental Activity or an Environmental
     Condition, regardless of whether based in contract, tort, implied or
     express warranty, strict liability, Environmental Requirement, or
     otherwise:  all liabilities, losses, judgments, damages, punitive damages,
     consequential damages, treble damages, costs and expenses (including,
     without limitation, the reasonable fees and disbursements of legal counsel
     and environmental consultants, all costs related to the performance of any
     required or necessary assessments, investigations, remediation, response,
     containment, closure, restoration, repair, cleanup, or detoxification of
     any Subject Property or any part thereof, the preparation and
     implementation of any maintenance, monitoring, closure, remediation,
     abatement, or other plans required by an Environmental Agency or by
     Environmental Requirements and any other costs recovered or recoverable
     under any Environmental Requirement), fines, penalties, or monetary
     sanctions.  Environmental Costs shall include without limitation:  (i)
     damages for personal injury or death, or injury to property or to natural
     resources; (ii) damage to the Subject Property or damage resulting from the
     loss of the Use of all or any part of the Subject Property, including but
     not limited to business loss; (iii) the cost of any demolition, rebuilding,
     or repair of the Subject Property or other property, required by
     Environmental Requirements  or necessary to restore the Subject Property or
     such other property to its condition prior to damage caused by an
     Environmental Condition, Environmental Activity, or by the remediation of
     an Environmental Activity, or by the remediation of an Environmental
     Condition or Environmental Activity; and (iv) diminution in value of the
     Subject Property or other property.

          (r) "Environmental Requirements" means all laws, ordinances, statutes,
     codes, rules, regulations, agreements, judgments, orders, and decrees now
     or hereafter enacted, promulgated, or amended, of the United States, the
     states, the counties, the cities, or any other political subdivisions in
     which a Subject Property is located, and any other political subdivision,
     agency, or instrumentality exercising jurisdiction over any of the United
     Cities Entities, any Subject Property, or the Use of the Subject Property,
     relating to pollution, the protection or regulation of human health,
     natural resources, or the environment, or the emission, discharge, release
     or threatened release of pollutants, contaminants, chemicals, or
     industrial, toxic, or hazardous substances or waste or Hazardous Materials
     into the environment

                                      50

<PAGE>
 
     (including, without limitation, ambient air, surface water, ground water,
     or land or soil).

          (s) "ERISA" means the Employee Retirement Income Security Act of 1974,
     as amended.

          (t) "Exchange Act" means the Securities Exchange Act of 1934, as
     amended.

          (u) "Governmental Authorizations" has the meaning set forth in Section
     1.1(a) above.

          (v) "Group Member" means any member of any "affiliated service group,"
     as defined in Section 414(m) of the Code, that includes any United Cities
     Entity or Atmos Entity, as the case may be, any member of any "controlled
     group of corporations," as defined by Section 1563 of the Code, that
     includes any United Cities Entity or Atmos Entity, as the case may be, or
     any member of any group of "trades or businesses under common control," as
     defined in Section 414(c) of the Code, that includes any United Cities
     Entity or Atmos Entity, as the case may be.

          (w) "Hart-Scott-Rodino Act" means the Hart-Scott-Rodino Antitrust
     Improvements Act of 1976, as amended.

          (x) "Hazardous Material" means any substance which is or contains (i)
     any "hazardous substance" as now or hereafter defined in (S) 101(14) of the
     Comprehensive Environmental Response, Compensation, and Liability Act of
     1980, as amended ("CERCLA") (42 U.S.C. (S) 9601 et seq.) or any regulations
     promulgated under CERCLA; (ii) any "hazardous waste" as now or hereafter
     defined in the Resource Conservation and Recovery Act (42 U.S.C. (S) 6901
     et seq.) ("RCRA") or regulations promulgated under RCRA; (iii) any
     substance regulated by the Toxic Substances Control Act (15 U.S.C. (S) 2601
     et seq.); (iv) gasoline, diesel fuel, or other petroleum hydrocarbons; (v)
     asbestos and asbestos containing materials, in any form, whether friable or
     non-friable; (vi) polychlorinated biphenyls; or (vii) radon gas; and any
     additional substances or materials which are now or hereafter classified or
     considered to be hazardous or toxic under Environmental Requirements or the
     common law, or any other applicable laws relating to the Subject Property.
     Hazardous Materials shall include, without limitation, any substance, the
     presence of which on any Subject Property (A) requires reporting,
     investigation, or remediation under Environmental Requirements; (B) causes
     or threatens to cause a nuisance on any Subject Property or adjacent
     property or poses or threatens to pose a hazard to the health or safety of
     persons on any Subject Property or adjacent property; or (C) which, if it
     emanated or migrated from the Subject Property, could constitute a
     trespass.

                                      51

<PAGE>
 
          (y) "Indemnified Parties" has the meaning set forth in Section 4.10
     above.

          (z) "Initial Environmental Inspection Period" has the meaning set
     forth in Section 3.4(a) above.

          (aa) "IRS" means the Internal Revenue Service.

          (bb) "Material" with respect to United Cities means that the effect of
     any untrue statement, misrepresentation or omission of United Cities
     contained in this Agreement on, or of any breach or failure to perform by
     United Cities of any of its covenants, warranties, agreements or
     obligations contained in this Agreement on, or the occurrence of any event
     affecting, the business, operations, properties, conditions (financial or
     otherwise), assets or liabilities of United Cities that result,
     individually or in the aggregate, in an reduction on a pro forma basis of
     $2,000,000 or more in the net profit of United Cities on an annualized
     basis for a twelve (12)-month period, or a reduction on a pro forma basis
     of $12,500,000 or more in the stockholders equity of United Cities as of
     the most recent audited balance sheet; provided, however, that no amounts
     shall be included in determining the foregoing amounts which arise with
     respect to any former manufactured gas plant site or the Kansas Department
     of Health and Environment mercury meter proceeding, except to the extent
     that such amounts arise from events or occurrences arising after the
     Initial Environmental Inspection Period; provided, further, that for
     purposes of calculating any such effect on the net profit of United Cities,
     there shall not be taken into account any item that would reduce such net
     profit on a pro forma basis by less than $5,000.  In the event of any
     dispute between the parties as to the determination of whether any such
     matter is Material, the parties agree to submit such dispute to Arthur
     Andersen LLP ("AA") and Ernst & Young LLP ("EY") for resolution on a joint
     basis.  In the event AA and EY are unable to resolve such dispute within
     ten (10) days, then the parties agree to submit the dispute to Coopers &
     Lybrand LLC whose determination shall be final and binding on the parties.

          (cc) "Material" with respect to Atmos means that the effect of any
     untrue statement, misrepresentation or omission of Atmos contained in this
     Agreement on, or of any breach or failure to perform by Atmos of any of its
     covenants, warranties, agreements or obligations contained in this
     Agreement on, or the occurrence of any event affecting, the business,
     operations, properties, conditions (financial or otherwise), assets or
     liabilities of Atmos that result, individually or in the aggregate, in an
     reduction on a pro forma basis of $2,000,000 or more in the net profit of
     Atmos on an annualized basis for a twelve (12)-month period, or a reduction
     on a pro forma basis of $12,500,000 or more in the stockholders equity of
     Atmos as of the most recent audited balance sheet; provided, however, that
     for purposes of calculating any such effect on the net profit of Atmos,
     there shall not be taken into account any item that would reduce such net
     profit on a pro forma basis by less than $5,000.  In the

                                      52

<PAGE>
 
     event of any dispute between the parties as to the determination of whether
     any such matter is Material, the parties agree to submit such dispute to
     Arthur Andersen LLP ("AA") and Ernst & Young LLP ("EY") for resolution on a
     joint basis.  In the event AA and EY are unable to resolve such dispute
     within ten (10) days, then the parties agree to submit the dispute to
     Coopers & Lybrand LLC whose determination shall be final and binding on the
     parties.

          (dd) "Merger" and "Plan of Merger" have the meanings set forth in
     Section 5.1(a)  above.

          (ee) "Nasdaq" means the Nasdaq National Market.

          (ff) "NYSE" means the New York Stock Exchange.

          (hh) "PBGC" means the Pension Benefit Guaranty Corporation.

          (ii) "Plan" means at any time any employee benefit plan as defined in
     Section 3(3) of ERISA (i) which is either (1) maintained by a United Cities
     Entity (or an Atmos Entity, as the case may be) or any Group Member or (2)
     maintained pursuant to a collective bargaining agreement or any other
     arrangement under which more than one employer makes contributions and (ii)
     to which any of the United Cities Entities (or Atmos Entities, as the case
     may be) or any Group Member is then making or accruing an obligation to
     make contributions or has within the preceding five plan years made
     contributions.

          (jj) "Proxy Statement/Prospectus" means the joint proxy which
     constitutes (i) a proxy statement to be delivered to Atmos' shareholders in
     connection with the Atmos Shareholders Meeting, (ii) a registration
     statement on Form S-4 to be filed by Atmos with the SEC to register the
     Atmos Stock that will be received by the shareholders of United Cities in
     the Merger, and (iii) a joint proxy statement and prospectus to be
     delivered to United Cities' shareholders in connection with the Atmos Stock
     and the United Cities' Shareholders Meeting with respect to the Merger.

          (kk) "PUHCA" means the Public Utility Holding Company Act of 1935, as
     amended.

          (ll) "Sampling" has the meaning set forth in Section 3.4(a) above.

          (mm) "Scope" has the meaning set forth in Section 3.4(a) above.

          (nn) "SEC" means the Securities and Exchange Commission.

                                      53

<PAGE>
 
          (oo) "Securities Act" means the Securities Act of 1933, as amended.

          (pp) "Standstill Agreement" means the Standstill Agreement dated as of
     July 13, 1996 by and between United Cities and Atmos.

          (qq) "Subject Property" means the real property currently or formerly
     Used by any of the United Cities Entities or any of their current or former
     subsidiaries and all improvements, fixtures, equipment, and personal
     property now or hereafter located on such real property.

          (rr) "Taxes" means all taxes, charges, fees, levies, imports, or other
     assessments by any federal, state, local, or foreign taxing authority,
     including, but not limited to, income, excise, property, sales, transfer,
     employment, payroll, franchise, and withholding taxes, and any interest,
     penalties, or additions attributable thereto, imposed thereon, or with
     respect thereof.

          (ss) "Tax Returns" means any return, report, information return, or
     other document (including any related or supporting information) filed or
     required to be filed with any federal, state, local, or foreign taxing
     authority in connection with the determination, assessment, or collection
     of any Tax.

          (tt) "United Cities Pension Plan" means the Retirement Plan for
     Employees of United Cities.

          (uu) "United Cities SEC Reports" has the meaning set forth in Section
     1.9(a)  above.

          (vv) "United Cities Shareholders Meeting" means the special meeting of
     United Cities' shareholders called for the purpose of considering and
     voting upon the Merger in accordance with and pursuant to the terms and
     provisions of this Agreement.

          (ww) "Use" means use, ownership, tenancy, development, construction,
     maintenance, management, operation, or occupancy and when referring to Use
     by United Cities shall also be deemed to include Use by the United Cities
     Subsidiaries or any other current or former subsidiaries of any of the
     United Cities Entities.

     Section 8.2  Non-Survival of Representations, Warranties, and Agreements.
     -----------  -----------------------------------------------------------  
The representations, warranties, and agreements in this Agreement shall
terminate at the Effective Time or upon the termination of this Agreement
pursuant to Section 7.1, as the case may be, except that the agreements set
forth in Sections 4.7, 4.8, 4.9, 4.10 and 5.4 shall survive the Merger or the
termination of this Agreement.

                                      54

<PAGE>
 
     Section 8.3  Notices.  All notices and other communications given or made
     -----------  -------                                                     
pursuant hereto shall be in writing and shall be deemed to have been duly given
or made as of the date delivered or mailed if delivered personally or by
facsimile or mailed by registered or certified mail (postage prepaid, return
receipt requested) to the parties at the following addresses (or at such other
address for a party as shall be specified by like notice):

          (a)  If to Atmos :

               Atmos Energy Corporation
               P.O. Box 650205
               Dallas, Texas  75265-0205
               Attention:  Mr. Robert F. Stephens

               With a copy to:

               Locke Purnell Rain Harrell (A Professional Corporation)
               2200 Ross Avenue, Suite 2200
               Dallas, Texas  75201-6776
               Attention:  Mr. Dan Busbee

          (b)  If to United Cities:

               United Cities Gas Company
               5300 Maryland Way
               Brentwood, Tennessee  37207
               Attention:  Mr. James B. Ford

               With a copy to:

               Chapman and Cutler
               111 West Monroe Street
               Chicago, Illinois  60603
               Attention:  Mr. Terence O'Meara

     Section 8.4  Assignment.  This Agreement is not assignable by any of the
     -----------  ----------                                                 
parties hereto.

     Section 8.5  Severability.  If any term or other provision of this
     -----------  ------------                                         
Agreement is invalid,  illegal, or incapable of being enforced by any rule of
law or public policy, all other conditions and provisions of this Agreement
shall nevertheless remain in full force and effect so long as the economic or
legal substance of the transactions contemplated hereby is not affected in any
manner adverse to any party.  Upon such determination that any term or other
provision is invalid, illegal, or incapable of being enforced, the parties
hereto shall negotiate

                                      55

<PAGE>

in good faith to modify this Agreement so as to effect the original intent of
the parties as closely as possible in an acceptable manner to the end that the
transactions contemplated hereby are fulfilled to the extent possible.

     Section 8.6  Parties in Interest.  This Agreement shall be binding upon and
     -----------  -------------------                                           
inure solely to the benefit of each party hereto, and nothing in this Agreement,
express or implied, is intended to or shall confer upon any other person any
right, benefit, or remedy of any nature whatsoever under or by reason of this
Agreement other than officers, directors and employees of United Cities who are
third party beneficiaries pursuant to Sections 4.7, 4.9 and 4.10.

     Section 8.7  Entire Agreement.  This Agreement constitutes the entire
     -----------  ----------------                                        
agreement and supersedes all prior agreements and undertakings (other than the
Confidentiality Agreement and the Standstill Agreement, both  between Atmos and
United Cities, which shall survive in accordance with their respective terms),
both written and oral, between the parties, with respect to the subject matter
hereof and is not intended to confer upon any other person any rights or
remedies hereunder.

     Section 8.8  Specific Performance.  The parties hereto agree that, if for
     -----------  --------------------                                        
any reason any party hereto shall have failed to perform its obligations under
this Agreement, then the other party hereto seeking to enforce this Agreement
against such non-performing party shall be entitled to specific performance and
injunctive and other equitable relief, and the parties hereto further agree to
waive any requirement for the securing or posting of any bond in connection with
the obtaining of any such injunctive or other equitable relief.  This provision
is without prejudice to any other rights that any party hereto may have against
the other party hereto for any willful failure to perform its obligations under
this Agreement.

     Section 8.9  Governing Law.  This Agreement shall be governed by, and
     -----------  -------------                                           
construed in accordance with, the laws of the State of Texas; provided, however,
that all provisions of this Agreement relating to (a) the rights, duties and
conduct of Board of Directors of United Cities with respect to this Agreement
and the transactions hereby, pursuant to Sections 3.2 and 3.11 hereof and (b)
whether Atmos shall be required to be an Illinois corporation as the survivor
under Merger, shall be governed by, and construed in accordance with the laws of
the State of Illinois.

     Section 8.10  Construction; Headings.  The parties hereto have participated
     ------------  ----------------------                                       
jointly in the negotiation and drafting of this Agreement.  In the event an
ambiguity or question of intent or interpretation arises, this Agreement shall
be construed as if drafted jointly by the parties and no presumption or burden
of proof shall arise favoring or disfavoring any party by virtue of the
authorship of any of the provisions of this Agreement.  The headings contained
in this Agreement are for reference purposes only and shall not affect in any
way the meaning or interpretation of this Agreement.

                                      56

<PAGE>
 
     Section 8.11  Incorporation of Exhibits.  The Exhibits identified in this
     ------------  -------------------------                                  
Agreement are incorporated herein by reference and made a part hereof for all
purposes.

     Section 8.12  Counterparts.  This Agreement may be executed in
     ------------  ------------                                    
counterparts, each of which will be an original, but all of which together will
constitute one and the same agreement.

     IN WITNESS WHEREOF, Atmos and United Cities have executed this Agreement
and Plan of Reorganization on the date first written above by their respective
officers thereunto duly authorized.

                              ATMOS ENERGY CORPORATION



                              By: /s/ Robert F. Stephens
                                  ------------------------------------
                                  Robert F. Stephens
                                  President and Chief Operating Officer



                              UNITED CITIES GAS COMPANY



                              By: /s/ Gene C. Koonce
                                  ------------------------------------
                                  Gene C. Koonce
                                  President and Chief Executive Officer

                                      57

<PAGE>
 
                                                                       EXHIBIT D


                                 PLAN OF MERGER


          This PLAN OF MERGER (this "Plan") by and between ATMOS ENERGY
CORPORATION, a Texas corporation ("Atmos"), and UNITED CITIES GAS COMPANY, an
Illinois and Virginia corporation ("United Cities").  Pursuant to this Plan,
United Cities shall be merged with and into Atmos, with Atmos as the surviving
corporation (the "Merger"), and the outstanding capital stock of United Cities
shall be converted into the right to receive shares of capital stock of Atmos.

                              W I T N E S S E T H:

          WHEREAS, Atmos is a corporation duly organized and existing under the
laws of the State of Texas, and United Cities is a corporation duly organized
and existing under the laws of the States of Illinois and Virginia;

          WHEREAS, Atmos and United Cities have entered into an Agreement and
Plan of Reorganization dated July 19, 1996 (the "Reorganization Agreement"),
which contemplates the merger of United Cities with and into Atmos, with Atmos
as the surviving corporation as provided in this Plan; and

          WHEREAS, the respective Boards of Directors of Atmos and United Cities
have duly authorized the execution of this Plan and have directed that the
Merger be submitted to their respective shareholders for a vote in accordance
with the requirements of the Texas Business Corporation Act, the Illinois
Business Corporation Act, and the Virginia Stock Corporation Act, the Boards of
Directors and shareholders of Atmos and United Cities have approved the Merger,
and the Board of Directors and shareholders of Atmos have authorized the
issuance of shares of the common stock, no par value, of Atmos (the "Common
Stock") in connection with the Merger;

          NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements herein contained, the parties hereto agree as follows:

                                   ARTICLE I

                       MERGER OF UNITED CITIES INTO ATMOS

          SECTION 1.01  The Merger.  In accordance with the Texas Business
Corporation Act, the Illinois Business Corporation Act, and the Virginia Stock
Corporation Act, United Cities shall be merged with and into Atmos at the
effective time of the Merger (the "Effective Time").  

                                      D-1
<PAGE>
 
Following the Merger, the separate corporate existence of United Cities
shall cease and Atmos shall be the surviving corporation, organized under the
laws of the States of Texas and Virginia (the "Surviving Corporation").

     SECTION 1.02 Effects of the Merger.

               (a)  The Merger shall have the effects set forth in the
     applicable provisions of the Texas Business Corporation Act, the Illinois
     Business Corporation  Act, and the Virginia Stock Corporation Act.  Without
     limiting the generality of the foregoing sentence, and subject thereto, at
     the Effective Time, by operation of law, all of the property, rights,
     privileges, powers and franchises of United Cities and Atmos shall vest in
     the Surviving Corporation, and all debts, liabilities and obligations of
     United Cities and Atmos shall be assumed by the Surviving Corporation and
     shall become the debts, liabilities and obligations of the Surviving
     Corporation.

               (b) If, at any time after the Merger, the Surviving Corporation
     shall deem it necessary to obtain further assignments or documents to vest,
     perfect, confirm or record in the Surviving Corporation title to any
     property or rights of United Cities acquired as a result of the Merger,
     United Cities hereby authorizes the officers and directors of the Surviving
     Corporation or its successors to execute and deliver on behalf of and in
     the name of United Cities all such proper deeds, assignments and other
     instruments and to do all things necessary and proper to vest, perfect,
     confirm or record title to such property or rights in the Surviving
     Corporation or its successor.

     SECTION 1.03  Articles of Incorporation; Bylaws.

               (a) The Restated Articles of Incorporation of Atmos, as in effect
          immediately prior to the Effective Time, shall be amended as provided
          herein, and such Restated Articles of Incorporation, as so amended,
          shall be the Articles of Incorporation of the Surviving Corporation,
          without any other modification or amendment until thereafter amended
          as provided by law.

               (b) The text of Article II of the Restated Articles of
          Incorporation of Atmos shall be amended and restated in its entirety
          to read as follows:

                    "The purpose for which the Corporation is organized is the
               transaction of any or all lawful business for which corporations
               may be incorporated under the Texas Business Corporation Act and
               the Virginia Stock Corporation Act, including, but not limited
               to, the following:  the transportation and distribution of
               natural gas by pipeline as a public utility."

                                      D-2
<PAGE>
 
               (c) There is hereby added to the Restated Articles of
          Incorporation of Atmos the following new Article VIII, the text of
          which is set forth below in its entirety:

                                 "ARTICLE VIII

                    These Articles of Incorporation may be amended only upon the
               affirmative vote of more than two-thirds of the outstanding
               shares of Common Stock of the Corporation entitled to vote
               thereon."

               (d) The Bylaws of Atmos, as in effect immediately prior to the
          Effective Time, shall be the Bylaws of the Surviving Corporation,
          without any modification or amendment until thereafter amended as
          provided by law.

     SECTION 1.04  Directors and Officers.

               (a) At the Effective Time, the number of directors of the
     Surviving Corporation shall be fifteen (15), and thereafter shall be set in
     the manner provided in the Bylaws of the Surviving Corporation.  The
     directors of the Surviving Corporation shall be the eleven (11) directors
     of Atmos in office at and as of the Effective Time and the following four
     (4) former directors of United Cities:  Messrs. Gene C. Koonce, __________,
     __________, and __________.  Each of the Atmos directors in office prior to
     the Effective Time shall continue to serve in the class and for the term
     that he was serving at and as of the Effective Time, and the following
     directors shall serve in the classes and for the terms indicated:  Mr.
     Koonce (Class I, with a term expiring in 1999); Mr. __________, (Class I,
     with a term expiring in 1999); Mr. __________ (Class II, with a term
     expiring in 1997); and Mr. __________ (Class III, with a term expiring in
     1998).  All of such directors shall remain in office until their respective
     successors are duly elected or appointed and qualified.

               (b) The officers of Atmos in office at and as of the Effective
     Time shall remain the officers of the Surviving Corporation, in each case
     until their respective successors are duly elected or appointed and
     qualified.

                                   ARTICLE II

                       CONVERSION AND EXCHANGE OF SHARES

     SECTION 2.01  Conversion of Shares.  (a)  At and as of the Effective Time,
each outstanding share of the common stock of United Cities (the "United Cities
Stock") automatically shall become and be converted into the right to receive
one (1) share of Common Stock (as the same may be adjusted in accordance with
the terms hereof).  The exchange ratio set forth in the 

                                      D-3
<PAGE>
 
immediately preceding sentence shall be appropriately and proportionately
adjusted in the event of any stock dividend on, or stock split or stock
combination of, or any other like change in the Common Stock or the United
Cities Stock based on a record date occurring during the period from July 19,
1996 until immediately prior to the Effective Time.

               (b) At and as of the Effective Time, each share of the United
     Cities Stock then held in the treasury of United Cities, if any, shall, by
     virtue of the Merger and without any action on the part of the holder
     thereof, be cancelled without payment of any consideration therefor and
     without any conversion thereof.

               (c) No fraction of a share of Common Stock will be issuable upon
     the conversion of shares of United Cities Stock in the Merger.  Instead,
     each shareholder of United Cities who but for this provision would be
     entitled to a fractional share of Common Stock shall, upon surrender to
     Atmos' Paying Agent (as hereinafter defined) of his certificate or
     certificates formerly representing shares of United Cities Stock (each, an
     "Old Certificate"), receive in lieu of such fractional share, and without
     interest, a cash amount determined by multiplying such fraction by the
     average of the closing sale  prices for a share of Common Stock, as
     reported on the NYSE, for the five (5) business days prior to the date on
     which the Effective Time shall occur.

     SECTION 2.02  Exchange of Certificates.  (a)  Following the Effective Time,
the shareholders of United Cities shall deliver to the Paying Agent their Old
Certificates.  Upon surrender to the Paying Agent of outstanding Old
Certificates, the holder of such Old Certificate or Old Certificates shall
receive in exchange therefor a certificate (a "New Certificate") representing
whole shares of the Common Stock (the "Atmos Shares") and cash in lieu of
fractional shares in accordance with the provisions of Sections 2.01(a) and
2.01(c) of this Plan.  Until so surrendered and exchanged, each Old Certificate
shall be deemed at and after the Effective Time to represent only the right to
receive upon such surrender a New Certificate representing Atmos Shares and cash
in lieu of fractional shares without any interest thereon.  All rights to
receive the Atmos Shares into which the shares of United Cities Stock are
converted, and cash in lieu of fractional shares, pursuant to this Plan shall be
deemed to have been issued and paid in full satisfaction of all rights
pertaining to such United Cities Stock.

               (b) The New Certificates representing the Atmos Shares to be
     issued in connection with the Merger shall in each case be issued to the
     person in whose name the surrendered Old Certificate or Old Certificates is
     or are registered.  A restrictive legend shall be placed on the New
     Certificates representing those Atmos Shares issued to persons who (i) were
     affiliates of United Cities prior to the Merger, and/or (ii) become
     affiliates of Atmos after the Merger, and a notation shall be made
     in the appropriate records of Atmos, indicating that the shares represented
     thereby are subject to certain restrictions on transfer.

                                      D-4
<PAGE>
 
               (c) At the Effective Time, the stock transfer books of United
     Cities shall be closed, and there shall be no further registration or
     transfers of shares of United Cities Stock thereafter in the records of
     United Cities.

               (d) Unless and until an Old Certificate shall be surrendered to
     the Paying Agent as set forth herein, the holder of such Old Certificate
     shall not receive any dividends or other distributions payable to record
     holders of the Common Stock.  Upon and after such surrender, there shall be
     paid (without interest) to the record holder of the New Certificate issued
     and exchanged for such Old Certificate, the amount of any such dividend or
     other distribution (the record date for the payment of which was after the
     Effective Time) not previously paid to such holder.  Holders of New
     Certificates who shall have surrendered their Old Certificates prior to any
     dividend record date will receive their dividends on the corresponding
     payment date.

               (e) The Atmos Shares issuable in the Merger are hereinafter
     called the "Merger Consideration."  Immediately following the Effective
     Time, Atmos shall deposit or cause to be deposited in trust with a bank or
     trust company to be designated by Atmos (the "Paying Agent"), as agent for
     the holders of the Old Certificates, the certificates representing the
     Atmos Shares that constitute the Merger Consideration.  As soon as
     practicable after the Effective Time, the Paying Agent shall cause to be
     mailed, and shall make available at the offices of the Paying Agent, to
     each person entitled to receive the Merger Consideration, a form of a
     letter of transmittal and instructions for use in effecting the surrender
     for payment of the Old Certificates which, immediately prior to the
     Effective Time, represented shares of United Cities Stock.  Upon surrender
     to the Paying Agent of such Old Certificates, together with such letter of
     transmittal, duly executed and completed in accordance with the
     instructions thereto, the Paying Agent shall promptly deliver the Merger
     Consideration to the persons entitled thereto, less any amount required to
     be withheld under applicable federal income tax regulations.  If payment is
     to be made to a person other than the registered holder of the Old
     Certificate surrendered, it shall be a condition of such payment that the
     Old Certificate so surrendered shall be properly endorsed or otherwise be
     in proper form for transfer and that the person requesting such payment
     shall pay any transfer taxes required by reason of the payment to a person
     other than the registered holder of the Old Certificate surrendered or
     establish to the satisfaction of Atmos and the Paying Agent that such tax
     has been paid or is not applicable.  The Paying Agent shall be authorized
     to deliver the Merger Consideration with respect to any Old Certificate for
     United Cities Stock theretofore issued which has been lost or destroyed,
     upon receipt of evidence satisfactory to Atmos and the Paying Agent of
     ownership of the United Cities Stock represented thereby and of appropriate
     indemnification.  One year
     following the Effective Time, Atmos, as the surviving corporation in the
     Merger, shall be entitled to require the Paying Agent to deliver to Atmos
     any certificates representing United Cities Stock which have not been
     disbursed to holders of Old Certificates representing United Cities Stock
     outstanding immediately prior to the Effective Time, and thereafter such
     holders shall be entitled to look only to Atmos (subject to abandoned

                                      D-5
<PAGE>
 
     property, escheat, or other similar laws) for the New Certificates
     representing Atmos Shares payable upon due surrender of their Old
     Certificates representing United Cities Stock.  Atmos shall pay all charges
     and expenses, including those of the Paying Agent, in connection with the
     exchange of the Merger Consideration for certificates representing United
     Cities Stock.

     SECTION 2.03.  Dissenting Shares.  Notwithstanding anything in this Plan to
the contrary, shares of United Cities Stock that are issued and outstanding
immediately prior to the Effective Time and that are held by a holder of United
Cities Stock who has not voted such shares in favor of adoption of this Plan and
shall have properly demanded dissenters' rights for such shares in the manner
provided in Section 11.70(a) of the Illinois Business Corporation Act ("United
Cities Dissenting Shares") shall not be converted into the right to receive the
Merger Consideration unless and until such holder becomes ineligible for such
dissenters' rights.  If such holder becomes ineligible for such dissenters'
rights, then, as of the Effective Time or the occurrence of such event,
whichever occurs last, such shares shall thereupon cease to be United Cities
Dissenting Shares and shall be converted into the right to receive the Merger
Consideration as provided in Section 2.01 hereof.

     SECTION 2.04  Treatment of United Cities Options.  Following the
consummation of the Merger, Atmos agrees to continue in effect the United Cities
Gas Company Long-Term Stock Plan of 1989, as amended.  Persons holding options
under such plan shall be allowed to exercise their options for Common Stock at
the exchange rate set forth in Section 2.01.  Persons holding stock appreciation
rights under such plan shall be allowed to exercise such rights based on the
price of Common Stock taking into account the exchange rate set forth in Section
2.01.


                                  ARTICLE III

                                 EFFECTIVE TIME

     SECTION 3.01.  Effective Time.  The Merger shall become effective in Texas
upon the issuance by the Secretary of State of Texas of a Certificate of Merger,
in Illinois upon the issuance by the Secretary of State of Illinois of a
Certificate of Merger and in Virginia upon the issuance by the Secretary of
State of Virginia of a Certificate of Merger.

     SECTION 3.02   Amendment.  At any time before the approval of the
Reorganization Agreement and this Plan by the respective shareholders of Atmos
and United Cities and prior to the Effective Time, the Reorganization Agreement
and this Plan may be amended in writing by Atmos and United Cities; provided,
however, that after approval by the shareholders of either party to the Merger,
no amendment may be made which would increase or decrease the amount or change
the type of consideration into which each share of United Cities Stock shall be
converted upon consummation of the Merger. This Plan may not be amended except
by an instrument in writing signed by the parties hereto.

                                      D-6

<PAGE>
 
                                                                   Exhibit 2.2

                               List of Exhibits
                           Omitted from Exhibit 2.1,
                      Agreement and Plan of Reorganization

1.   Exhibit A, United Cities Gas Company Disclosure Schedule, containing
     information regarding United Cities' subsidiaries, capitalization, required
     consents, debt instruments, compliance with laws and agreements,
     environmental matters, material contracts, litigation, liens and
     encumbrances on assets, taxes, employee benefit plans, labor matters, and
     other matters.

2.   Exhibit B, Atmos Energy Corporation Disclosure Schedule, containing
     information regarding Atmos' capitalization, required consents, debt
     instruments, material contracts, litigation, liens and encumbrances on
     assets, employee benefit plans, and other matters.

3.   Exhibit C-1, Form of Employment Agreement to be entered into by and between
     Atmos and James B. Ford

4.   Exhibit C-2, Form of Employment Agreement to be entered into by and between
     Atmos and Thomas R. Blose

5.   Exhibit C-3, Form of Employment Agreement to be entered into by and between
     Atmos and Gene C. Koonce

     Atmos Energy Corporation agrees to furnish supplementally to the Commission
     upon request a copy of any omitted exhibit.

<PAGE>
 
                                                                    EXHIBIT 20.1


                                 NEWS RELEASE
Atmos Energy Corporation                           [LOGO OF ATMOS APPEARS HERE]
P.O. Box 650205
Dallas, Texas 75265-0205
(214) 934-9227                                      
       DATE: July 22, 1996  ATMOS MEDIA CONTACT:  Margaret Watson
                                                  214/450-4050
FOR RELEASE: IMMEDIATELY  ATMOS INVESTOR/ANALYST  
                                     CONTACT:     Jack Eversull
                                                  214/788-3729
                        UNITED CITIES CONTACT:    Linda Kelley
                                                  615/373-0104, Ext. 224

              ATMOS ENERGY CORPORATION, UNITED CITIES GAS COMPANY
                    ANNOUNCE DEFINITIVE AGREEMENT TO MERGE

Dallas, Texas -- Atmos Energy Corporation (NYSE: ATO) and United Cities Gas 
Company (NASDAQ: UCIT) jointly announced today that the companies have reached a
definitive agreement for the acquisition by merger of United Cities by Atmos. 
Atmos will be the surviving entity following the merger.

Under the terms of the definitive agreement, one share of Atmos stock will be 
exchanged for each share of United Cities stock. No adjustment to the exchange 
ratio will be made to reflect changes in Atmos' stock price. Atmos has agreed to
increase the indicated annual dividend to not less than $1.02 per share at the 
first board meeting following the closing of the transaction. The current annual
Atmos dividend is $.96 per share. The transaction is expected to be tax-free to 
United Cities shareholders and accounted for as a pooling of interests. On June 
30, 1996, there were 15,982,304 shares of Atmos common stock outstanding and 
13,102,913 common shares of United Cities outstanding. Atmos' stock closed at 
$25.875 per share, and United Cities' stock closed at $17.00 per share on 
Friday, July 19.

The Board of Directors of the combined company will consist of all 11 current 
members of the Atmos board and four current members from the 10-member United 
Cities board. Charles K. Vaughan will remain chairman of the board of Atmos and 
will be the chief executive officer of Atmos. Gene C. Koonce, currently United 
Cities chairman of the board, president and chief executive officer, will become
vice chairman of the Atmos board. Robert F. Stephens will remain president and 
chief operating officer of Atmos, and James F. Purser will remain executive vice
president and chief financial officer. James B. Ford, currently senior vice 
president and treasurer of United Cities, will become senior vice president of 
finance for Atmos. Thomas R. Blose, currently senior vice president - 
operations and engineering of United Cities, will become president of United 
Cities Gas Company, a division of Atmos Energy Corporation, and vice president 
of Atmos.

The transaction is subject to approval by the shareholders of both companies. 
Approval by appropriate regulatory bodies also will be required.

United Cities, based in Brentwood, Tenn., is primarily a distributor of natural 
gas, serving approximately 310,000 natural gas customers in Tennessee, Illinois,
Missouri, Kansas, Iowa, Georgia, South Carolina, and Virginia, and has gas
storage facilities in Kentucky and Kansas. United Cities also serves about
25,000 propane customers in Tennessee, North Carolina and Virginia.

The combined entity would serve approximately 1 million customers in 13 states, 
making it one of the largest natural gas utilities in the U.S. based on number 
of customers.

"We welcome United Cities to the Atmos family of companies. This is a good fit 
- -- both companies have strong track records of internal growth and growth 
through acquisitions, as well as similar management philosophies," said Charles 
K. Vaughan, Atmos chairman of the board.

more....

                                       1

<PAGE>

"This transaction is consistent with Atmos' continuing long-term corporate 
development strategy of increasing the value of the company through external
growth," said Robert F. Stephens, president and chief operating officer of
Atmos. "We believe the transaction will be additive to earnings per share 
after the initial one-time cost and assimilation are completed. We believe
this merger will further position the company to be successful in the 
increasingly competitive environment for utilities because of our larger 
size and geographic diversity. United Cities' unregulated businesses also
complement Atmos' unregulated businesses."

"We are pleased to be joining the Atmos family of companies, and feel the
combination of Atmos and United Cities will result in a very strong company
that will continue to be successful in the future," said Gene C. Koonce, United 
Cities chairman of the board, president and chief executive officer.

Atmos acquired Trans Louisiana Gas Company in 1986, Western Kentucky Gas
Company in 1987, Greeley Gas Company in 1993, as well as several smaller
gas systems in Louisiana. The company has continued to aggressively search
for additional natural gas distribution properties. Since 1985, United Cities
has added approximately 180,000 new customers in its natural gas distribution
system through acquisitions and internal growth.

Atmos Energy Corporation, based in Dallas, Texas, currently provides natural gas
service to approximately 673,000 customers in Texas, Colorado, Kansas, Missouri,
Louisiana and Kentucky through its operating companies -- Energas Company, 
Greeley Gas Company, Trans Louisiana Gas Company and Western Kentucky Gas 
Company.

                  ATMOS AND UNITED CITIES COMBINED STATISTICS
                  From public documents as of March 31, 1996

                                  (Unaudited)
<TABLE> 
<CAPTION> 
                             Atmos     United Cities     Combined
                            -------    -------------     --------
OPERATIONAL
- -----------
<S>                           <C>        <C>                <C>             <C> 
No. of customers              673,000         335,000*      1,008,000
No. of employees                1,650           1,300           2,950
No. of states served                6              10              13

FINANCIAL
12 mos. ending 3/31/96
- ----------------------
(000's except per share)
Utility operating revenues   $482,250        $309,701         $791,951
Net plant in service         $387,379        $341,454         $728,833

COMMON STOCK
12 mos. ending 3/31/96
- ----------------------
Earnings                     $ 26,068        $ 13,982         $ 40,050
Earnings per share           $   1.67        $   1.14           
Cash flow                    $ 56,353        $ 36,067         $ 92,420
Cash flow per share          $   3.60        $   2.93
Av. shares outstanding         15,638          12,306           27,944

                                                                           % Total
                                                                           Capital.
                                                                           -------
Shareholders equity          $181,505        $161,283         $342,788        54%
Long term debt               $125,303        $162,998         $288,301        46%
Total capitalization         $306,808        $324,281         $631,089       100%
</TABLE> 

* includes propane customers

                              #     #     #


<PAGE>
 
                                                                    EXHIBIT 99.1


                              STANDSTILL AGREEMENT

     This STANDSTILL AGREEMENT (the "Agreement"), made and entered into by and
between ATMOS ENERGY CORPORATION, a Texas corporation ("Atmos"), and UNITED
CITIES GAS COMPANY, an Illinois and Virginia corporation ("United Cities"), and
effective as of this 13th day of July, 1996,

                              W I T N E S S E T H:

     WHEREAS, the parties hereto have entered into that certain Confidentiality
Agreement, dated July 5, 1996 (the "Confidentiality Agreement");

     WHEREAS, pursuant to the Confidentiality Agreement, the parties hereto are
evaluating a possible merger of United Cities and Atmos, subject to approval by
the boards of directors and shareholders of United Cities and Atmos (the
"Possible Transaction"); and

     WHEREAS, this Agreement is not intended to create any obligations for
either party hereto with respect to the Possible Transaction, other than the
agreements expressly set forth herein, and no other contract or agreement
providing for the Possible Transaction shall be deemed to exist between the
parties hereto.

     NOW, THEREFORE, for and in consideration of the premises and the agreements
herein contained, the sufficiency of which is hereby acknowledged, the parties
hereto agree as follows:

     1.  Standstill Provisions.  For a period of two years from the date of this
         ---------------------                                                  
Agreement, except as may otherwise be provided pursuant to the terms of a
written definitive agreement between the parties and approved by their
respective boards of directors with respect to the Possible Transaction
negotiated pursuant to the Confidentiality Agreement, neither party shall,
directly or indirectly:

               (a) acquire, or offer or agree to acquire, by purchase or
     otherwise, any securities or property of the other party (or direct or
     indirect rights or options to acquire any securities or property of the
     other party) except by way of stock, dividends or other distributions made
     on a pro rata basis with respect to securities of the other party acquired
     prior to the date of this Agreement;

               (b) solicit proxies or consents or become a participant in a
     "solicitation" (as such term is used in the Proxy Rules of the Securities
     and Exchange Commission) of proxies or consents with respect to securities
     of the other party with regard to any matter or otherwise act, alone or in
     concert with others, to seek to control or influence the management, board
     of directors or policies of the other party;

                                       1
<PAGE>
 
               (c) induce, attempt to induce or in any manner assist any other 
     person in initiating any stockholder proposal or a tender or exchange offer
     for securities of the other party or any change of control of the other
     party, or for the purpose of convening a stockholders' meeting of the other
     party;

               (d) make any public announcement or make any written or oral
     proposal or invitation to discuss any possibility, intention, plan or
     arrangement, relating to a tender or exchange offer for securities of the
     other party or a merger, consolidation or other business combination (or
     other similar transaction which should result in a change of control), sale
     of all or a substantial portion of the  assets of the other party,
     recapitalization, restructuring, liquidation, dissolution or other
     extraordinary corporate transaction between such party and any of its
     affiliates and the other party or take any action which might require the
     other party to make a public announcement regarding any of the foregoing;

               (e) deposit any securities of the other party in a voting trust
     or subject any securities of the other party to any arrangement or
     agreement with respect to the voting of securities of the other party;

               (f) form, join or in any way participate in a partnership,
     limited partnership, syndicate or other group (or otherwise act in concert
     with any other person) for the purpose of acquiring, holding, voting and
     disposing of securities of the other party or taking any other actions
     restricted or prohibited under clauses (a) through (e) of this paragraph,
     or announce an intention to do, or enter into any arrangement or
     understanding with others to do, any of the actions restricted or
     prohibited under clauses (a) through (e) of this paragraph; or

               (g) request the other party (or its directors, officers,
     employees or agents), to amend or waive any provision of this paragraph
     (including this subsection (g)), except as may otherwise be provided
     pursuant to the terms of a written definitive agreement between the parties
     and approved by their respective boards of directors with respect to the
     Possible Transaction negotiated pursuant to the Confidentiality 
     Agreement.

          2.   Exception to Standstill Provisions.
               ---------------------------------- 

               (a) Notwithstanding clauses (a), (e), and (f) of Paragraph 1
          above, the employee benefit plans of either party may acquire
          securities of the other party if the aggregate beneficial ownership of
          all such plans of such party does not exceed one percent (1%) of the
          outstanding securities of the same class of the other party.

               (b) Nothing in this Agreement shall preclude or prevent Atmos
          from making a counter-offer to acquire United Cities in the event that
          (A) prior to the earlier of (i) the termination of negotiations
          pursuant to the Confidentiality 

                                       2
<PAGE>
 
          Agreement relating to a Possible Transaction, or (ii) the execution of
          a definitive agreement between the parties and approved by the
          respective boards of directors providing for the Possible Transaction,
          a third party makes an unsolicited bona fide publicly announced offer
          to acquire control of United Cities pursuant to a tender offer,
          merger, consolidation, share exchange, purchase of a substantial
          portion of assets, business combination or other similar transaction
          (a "Third Party Offer") and (B) United Cities thereafter (i) issues a
          statement recommending the Third Party Offer to its shareholders or
          (ii) United Cities either issues a statement not recommending the
          Third Party Offer or takes no position with respect to such offer but
          is required by a court to furnish the party making the Third Party
          Offer a list of shareholders of United Cities.

          3.   No Further Agreement.  This Agreement constitutes the entire
               --------------------                                        
agreement between the parties hereto concerning the subject matter hereof.  This
Agreement does not constitute an offer to engage in any transaction, including
without limitation, the Possible Transaction, it does not impose any obligation
to bargain in good faith in connection therewith, and no party hereto intends to
be bound by any agreement concerning a Possible Transaction unless and until it
agrees to and signs a formal written contract approved by its board of
directors.  Either party may terminate discussions regarding the Possible
Transaction at any time, for any reason.  Each party is free to pursue any other
possible business transactions with any other persons at any time, and without
any obligations to notify the other party that any such transaction is being
considered, including any merger or other business combination.  No person may
reasonably rely on any promises inconsistent with this paragraph.

          4.   Binding Upon Successors.  This Agreement shall be binding upon
               -----------------------                                       
and inure to the benefit of (i) the successors in interest of each of the
parties hereto and (ii) any affiliate of any party hereto or any affiliate of
any such successor in interest.

          5.   Choice of Law.  This Agreement shall be governed by and in
               -------------                                             
accordance with the laws of the State of Illinois, without regard to the
conflict of laws principles thereof.

          IN WITNESS WHEREOF, the undersigned have executed this Standstill
Agreement as of the date first written above.


ATMOS ENERGY CORPORATION                UNITED CITIES GAS COMPANY



By: /s/ James F. Purser                  By: /s/ James B. Ford
    ------------------------------           -----------------------------
    James F. Purser                          James B. Ford
    Executive Vice President and             Senior Vice President and Treasurer
    Chief Financial Officer

                                       3


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